< draft-mavrogiannopoulos-ssl-version3   rfc6101.txt 
Network Working Group A. Freier Internet Engineering Task Force (IETF) A. Freier
Internet-Draft P. Karlton Request for Comments: 6101 P. Karlton
Intended status: Historic Netscape communications Category: Historic Netscape Communications
Expires: December 12, 2011 P. Kocher ISSN: 2070-1721 P. Kocher
Independent consultant Independent Consultant
June 10, 2011 August 2011
The SSL Protocol Version 3.0 The Secure Sockets Layer (SSL) Protocol Version 3.0
draft-mavrogiannopoulos-ssl-version3-06
Abstract Abstract
This document specifies Version 3.0 of the Secure Sockets Layer (SSL This document is published as a historical record of the SSL 3.0
V3.0) protocol, a security protocol that provides communications protocol. The original Abstract follows.
This document specifies version 3.0 of the Secure Sockets Layer (SSL
3.0) protocol, a security protocol that provides communications
privacy over the Internet. The protocol allows client/server privacy over the Internet. The protocol allows client/server
applications to communicate in a way that is designed to prevent applications to communicate in a way that is designed to prevent
eavesdropping, tampering, or message forgery. eavesdropping, tampering, or message forgery.
Foreword Foreword
Although the SSL 3.0 protocol is a widely implemented protocol, a Although the SSL 3.0 protocol is a widely implemented protocol, a
pioneer in secure communications protocols, and the basis for TLS it pioneer in secure communications protocols, and the basis for
was never formally published by IETF, except in several expired Transport Layer Security (TLS), it was never formally published by
internet-drafts. This allowed no easy referencing to the protocol. the IETF, except in several expired Internet-Drafts. This allowed no
We believe a stable reference to the original document should exist easy referencing to the protocol. We believe a stable reference to
and for that reason, this document describes what is known as the the original document should exist and for that reason, this document
last published version of the SSL 3.0 protocol. That is the November describes what is known as the last published version of the SSL 3.0
18, 1996 version of the protocol. protocol, that is, the November 18, 1996, version of the protocol.
There were no changes to the original document other than trivial There were no changes to the original document other than trivial
editorial changes and the addition of a "Security considerations" editorial changes and the addition of a "Security Considerations"
section. However portions of the original draft that no longer apply section. However, portions of the original document that no longer
were not included. Such are the "Patent statement" section, the apply were not included. Such as the "Patent Statement" section, the
"Reserved ports assignment" section and the cipher-suite registrator "Reserved Ports Assignment" section, and the cipher-suite registrator
note in the "The CipherSuite" section. The "US export rules" note in the "The CipherSuite" section. The "US export rules"
discussed in the document do not apply today but are kept intact to discussed in the document do not apply today but are kept intact to
provide context for decisions taken in protocol design. The "Goals provide context for decisions taken in protocol design. The "Goals
of This Document" section indicates the goals for adopters of SSL of This Document" section indicates the goals for adopters of SSL
3.0, not goals of the IETF. 3.0, not goals of the IETF.
The authors and editors were retained as in the original document. The authors and editors were retained as in the original document.
The editor of this document is Nikos Mavrogiannopoulos The editor of this document is Nikos Mavrogiannopoulos
(nikos.mavrogiannopoulos@esat.kuleuven.be). The editor would like to (nikos.mavrogiannopoulos@esat.kuleuven.be). The editor would like to
thank Dan Harkins, Linda Dunbar, Sean Turner, and Geoffrey Keating thank Dan Harkins, Linda Dunbar, Sean Turner, and Geoffrey Keating
for reviewing this document and providing helpful comments. for reviewing this document and providing helpful comments.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering This document is not an Internet Standards Track specification; it is
Task Force (IETF). Note that other groups may also distribute published for the historical record.
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months This document defines a Historic Document for the Internet community.
and may be updated, replaced, or obsoleted by other documents at any This document is a product of the Internet Engineering Task Force
time. It is inappropriate to use Internet-Drafts as reference (IETF). It represents the consensus of the IETF community. It has
material or to cite them other than as "work in progress." received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Not all documents
approved by the IESG are a candidate for any level of Internet
Standard; see Section 2 of RFC 5741.
This Internet-Draft will expire on December 12, 2011. Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc6101.
Copyright Notice Copyright Notice
Copyright (c) 2011 IETF Trust and the persons identified as the Copyright (c) 2011 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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modifications of such material outside the IETF Standards Process. modifications of such material outside the IETF Standards Process.
Without obtaining an adequate license from the person(s) controlling Without obtaining an adequate license from the person(s) controlling
the copyright in such materials, this document may not be modified the copyright in such materials, this document may not be modified
outside the IETF Standards Process, and derivative works of it may outside the IETF Standards Process, and derivative works of it may
not be created outside the IETF Standards Process, except to format not be created outside the IETF Standards Process, except to format
it for publication as an RFC or to translate it into languages other it for publication as an RFC or to translate it into languages other
than English. than English.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 5 1. Introduction ....................................................5
2. Goals . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 2. Goals ...........................................................5
3. Goals of this document . . . . . . . . . . . . . . . . . . . . 6 3. Goals of This Document ..........................................6
4. Presentation language . . . . . . . . . . . . . . . . . . . . 6 4. Presentation Language ...........................................6
4.1. Basic block size . . . . . . . . . . . . . . . . . . . . . 6 4.1. Basic Block Size ...........................................7
4.2. Miscellaneous . . . . . . . . . . . . . . . . . . . . . . 7 4.2. Miscellaneous ..............................................7
4.3. Vectors . . . . . . . . . . . . . . . . . . . . . . . . . 7 4.3. Vectors ....................................................7
4.4. Numbers . . . . . . . . . . . . . . . . . . . . . . . . . 8 4.4. Numbers ....................................................8
4.5. Enumerateds . . . . . . . . . . . . . . . . . . . . . . . 8 4.5. Enumerateds ................................................8
4.6. Constructed types . . . . . . . . . . . . . . . . . . . . 9 4.6. Constructed Types ..........................................9
4.6.1. Variants . . . . . . . . . . . . . . . . . . . . . . . 9 4.6.1. Variants ...........................................10
4.7. Cryptographic attributes . . . . . . . . . . . . . . . . . 11 4.7. Cryptographic Attributes ..................................11
4.8. Constants . . . . . . . . . . . . . . . . . . . . . . . . 11 4.8. Constants .................................................12
5. SSL protocol . . . . . . . . . . . . . . . . . . . . . . . . . 12 5. SSL Protocol ...................................................12
5.1. Session and connection states . . . . . . . . . . . . . . 12 5.1. Session and Connection States .............................12
5.2. Record layer . . . . . . . . . . . . . . . . . . . . . . . 13 5.2. Record Layer ..............................................14
5.2.1. Fragmentation . . . . . . . . . . . . . . . . . . . . 14 5.2.1. Fragmentation ......................................14
5.2.2. Record compression and decompression . . . . . . . . . 14 5.2.2. Record Compression and Decompression ...............15
5.2.3. Record payload protection and the CipherSpec . . . . . 15 5.2.3. Record Payload Protection and the CipherSpec .......16
5.3. Change cipher spec protocol . . . . . . . . . . . . . . . 18 5.3. Change Cipher Spec Protocol ...............................18
5.4. Alert protocol . . . . . . . . . . . . . . . . . . . . . . 18 5.4. Alert Protocol ............................................18
5.4.1. Closure alerts . . . . . . . . . . . . . . . . . . . . 19 5.4.1. Closure Alerts .....................................19
5.4.2. Error alerts . . . . . . . . . . . . . . . . . . . . . 20 5.4.2. Error Alerts .......................................20
5.5. Handshake protocol overview . . . . . . . . . . . . . . . 21 5.5. Handshake Protocol Overview ...............................21
5.6. Handshake protocol . . . . . . . . . . . . . . . . . . . . 23 5.6. Handshake Protocol ........................................23
5.6.1. Hello messages . . . . . . . . . . . . . . . . . . . . 24 5.6.1. Hello messages .....................................24
5.6.2. Server certificate . . . . . . . . . . . . . . . . . . 28 5.6.2. Server Certificate .................................28
5.6.3. Server key exchange message . . . . . . . . . . . . . 28 5.6.3. Server Key Exchange Message ........................28
5.6.4. Certificate request . . . . . . . . . . . . . . . . . 30 5.6.4. Certificate Request ................................30
5.6.5. Server hello done . . . . . . . . . . . . . . . . . . 31 5.6.5. Server Hello Done ..................................31
5.6.6. Client certificate . . . . . . . . . . . . . . . . . . 31 5.6.6. Client Certificate .................................31
5.6.7. Client key exchange message . . . . . . . . . . . . . 31 5.6.7. Client Key Exchange Message ........................31
5.6.8. Certificate verify . . . . . . . . . . . . . . . . . . 34 5.6.8. Certificate Verify .................................34
5.6.9. Finished . . . . . . . . . . . . . . . . . . . . . . . 35 5.6.9. Finished ...........................................35
5.7. Application data protocol . . . . . . . . . . . . . . . . 35 5.7. Application Data Protocol .................................36
6. Cryptographic computations . . . . . . . . . . . . . . . . . . 36 6. Cryptographic Computations .....................................36
6.1. Asymmetric cryptographic computations . . . . . . . . . . 36 6.1. Asymmetric Cryptographic Computations .....................36
6.1.1. RSA . . . . . . . . . . . . . . . . . . . . . . . . . 36 6.1.1. RSA ................................................36
6.1.2. Diffie-Hellman . . . . . . . . . . . . . . . . . . . . 36 6.1.2. Diffie-Hellman .....................................37
6.1.3. FORTEZZA . . . . . . . . . . . . . . . . . . . . . . . 37 6.1.3. FORTEZZA ...........................................37
6.2. Symmetric cryptographic calculations and the CipherSpec . 37 6.2. Symmetric Cryptographic Calculations and the CipherSpec ...37
6.2.1. The master secret . . . . . . . . . . . . . . . . . . 37 6.2.1. The Master Secret ..................................37
6.2.2. Converting the master secret into keys and MAC 6.2.2. Converting the Master Secret into Keys and
secrets . . . . . . . . . . . . . . . . . . . . . . . 37 MAC Secrets ........................................37
7. Security considerations . . . . . . . . . . . . . . . . . . . 39 7. Security Considerations ........................................39
8. IANA considerations . . . . . . . . . . . . . . . . . . . . . 39 8. Informative References .........................................40
9. Informative References . . . . . . . . . . . . . . . . . . . . 40 Appendix A. Protocol Constant Values ..............................42
Appendix A. Protocol constant values . . . . . . . . . . . . . . 41 A.1. Record Layer ...............................................42
A.1. Record layer . . . . . . . . . . . . . . . . . . . . . . . 41 A.2. Change Cipher Specs Message ................................43
A.2. Change cipher specs message . . . . . . . . . . . . . . . 43 A.3. Alert Messages .............................................43
A.3. Alert messages . . . . . . . . . . . . . . . . . . . . . . 43 A.4. Handshake Protocol .........................................44
A.4. Handshake protocol . . . . . . . . . . . . . . . . . . . . 43 A.4.1. Hello Messages .........................................44
A.4.1. Hello messages . . . . . . . . . . . . . . . . . . . . 44 A.4.2. Server Authentication and Key Exchange Messages ........45
A.4.2. Server authentication and key exchange messages . . . 45 A.5. Client Authentication and Key Exchange Messages ............46
A.5. Client authentication and key exchange messages . . . . . 47 A.5.1. Handshake Finalization Message .........................47
A.5.1. Handshake finalization message . . . . . . . . . . . . 48 A.6. The CipherSuite ............................................47
A.6. The CipherSuite . . . . . . . . . . . . . . . . . . . . . 48 A.7. The CipherSpec .............................................49
A.7. The CipherSpec . . . . . . . . . . . . . . . . . . . . . . 49 Appendix B. Glossary ..............................................50
Appendix B. Glossary . . . . . . . . . . . . . . . . . . . . . . 50 Appendix C. CipherSuite Definitions ...............................53
Appendix C. CipherSuite definitions . . . . . . . . . . . . . . . 53 Appendix D. Implementation Notes ..................................56
Appendix D. Implementation Notes . . . . . . . . . . . . . . . . 55 D.1. Temporary RSA Keys .........................................56
D.1. Temporary RSA keys . . . . . . . . . . . . . . . . . . . . 56 D.2. Random Number Generation and Seeding .......................56
D.2. Random Number Generation and Seeding . . . . . . . . . . . 56 D.3. Certificates and Authentication ............................57
D.3. Certificates and authentication . . . . . . . . . . . . . 57 D.4. CipherSuites ...............................................57
D.4. CipherSuites . . . . . . . . . . . . . . . . . . . . . . . 57 D.5. FORTEZZA ...................................................57
D.5. FORTEZZA . . . . . . . . . . . . . . . . . . . . . . . . . 57 D.5.1. Notes on Use of FORTEZZA Hardware ......................57
D.5.1. Notes on use of FORTEZZA hardware . . . . . . . . . . 57 D.5.2. FORTEZZA Cipher Suites .................................58
D.5.2. FORTEZZA Ciphersuites . . . . . . . . . . . . . . . . 58 D.5.3. FORTEZZA Session Resumption ............................58
D.5.3. FORTEZZA Session resumption . . . . . . . . . . . . . 58 Appendix E. Version 2.0 Backward Compatibility ....................59
Appendix E. Version 2.0 Backward Compatibility . . . . . . . . . 58 E.1. Version 2 Client Hello .....................................59
E.1. Version 2 client hello . . . . . . . . . . . . . . . . . . 59 E.2. Avoiding Man-in-the-Middle Version Rollback ..............61
E.2. Avoiding man-in-the-middle version rollback . . . . . . . 61 Appendix F. Security Analysis .....................................61
Appendix F. Security analysis . . . . . . . . . . . . . . . . . . 61 F.1. Handshake Protocol .........................................61
F.1. Handshake protocol . . . . . . . . . . . . . . . . . . . . 61 F.1.1. Authentication and Key Exchange ........................61
F.1.1. Authentication and key exchange . . . . . . . . . . . 61 F.1.2. Version Rollback Attacks ...............................64
F.1.2. Version rollback attacks . . . . . . . . . . . . . . . 64 F.1.3. Detecting Attacks against the Handshake Protocol .......64
F.1.3. Detecting attacks against the handshake protocol . . . 64 F.1.4. Resuming Sessions ......................................65
F.1.4. Resuming sessions . . . . . . . . . . . . . . . . . . 65 F.1.5. MD5 and SHA ............................................65
F.1.5. MD5 and SHA . . . . . . . . . . . . . . . . . . . . . 65 F.2. Protecting Application Data ................................65
F.2. Protecting application data . . . . . . . . . . . . . . . 65 F.3. Final Notes ................................................66
F.3. Final notes . . . . . . . . . . . . . . . . . . . . . . . 66 Appendix G. Acknowledgements ......................................66
Appendix G. Acknowledgements . . . . . . . . . . . . . . . . . . 66 G.1. Other Contributors .........................................66
G.1. Other contributors . . . . . . . . . . . . . . . . . . . . 66 G.2. Early Reviewers ............................................67
G.2. Early reviewers . . . . . . . . . . . . . . . . . . . . . 67
1. Introduction 1. Introduction
The primary goal of the SSL Protocol is to provide privacy and The primary goal of the SSL protocol is to provide privacy and
reliability between two communicating applications. The protocol is reliability between two communicating applications. The protocol is
composed of two layers. At the lowest level, layered on top of some composed of two layers. At the lowest level, layered on top of some
reliable transport protocol (e.g., TCP[RFC0793]), is the SSL Record reliable transport protocol (e.g., TCP [RFC0793]), is the SSL record
Protocol. The SSL Record Protocol is used for encapsulation of protocol. The SSL record protocol is used for encapsulation of
various higher level protocols. One such encapsulated protocol, the various higher level protocols. One such encapsulated protocol, the
SSL Handshake Protocol, allows the server and client to authenticate SSL handshake protocol, allows the server and client to authenticate
each other and to negotiate an encryption algorithm and cryptographic each other and to negotiate an encryption algorithm and cryptographic
keys before the application protocol transmits or receives its first keys before the application protocol transmits or receives its first
byte of data. One advantage of SSL is that it is application byte of data. One advantage of SSL is that it is application
protocol independent. A higher level protocol can layer on top of protocol independent. A higher level protocol can layer on top of
the SSL Protocol transparently. The SSL protocol provides connection the SSL protocol transparently. The SSL protocol provides connection
security that has three basic properties: security that has three basic properties:
o The connection is private. Encryption is used after an initial o The connection is private. Encryption is used after an initial
handshake to define a secret key. Symmetric cryptography is used handshake to define a secret key. Symmetric cryptography is used
for data encryption (e.g., DES[DES], RC4[RSADSI], etc.) for data encryption (e.g., DES [DES], 3DES [3DES], RC4 [SCH]).
o The peer's identity can be authenticated using asymmetric, or o The peer's identity can be authenticated using asymmetric, or
public key, cryptography (e.g., RSA[RSA], DSS[DSS], etc.). public key, cryptography (e.g., RSA [RSA], DSS [DSS]).
o The connection is reliable. Message transport includes a message o The connection is reliable. Message transport includes a message
integrity check using a keyed MAC. Secure hash functions (e.g., integrity check using a keyed Message Authentication Code (MAC)
SHA, MD5, etc.) are used for MAC computations. [RFC2104]. Secure hash functions (e.g., SHA, MD5) are used for
MAC computations.
2. Goals 2. Goals
The goals of SSL Protocol v3.0, in order of their priority, are: The goals of SSL protocol version 3.0, in order of their priority,
are:
1. Cryptographic security 1. Cryptographic security
SSL should be used to establish a secure connection between SSL should be used to establish a secure connection between
two parties. two parties.
2. Interoperability 2. Interoperability
Independent programmers should be able to develop applications Independent programmers should be able to develop applications
utilizing SSL 3.0 that will then be able to successfully utilizing SSL 3.0 that will then be able to successfully
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4. Relative efficiency 4. Relative efficiency
Cryptographic operations tend to be highly CPU intensive, Cryptographic operations tend to be highly CPU intensive,
particularly public key operations. For this reason, the SSL particularly public key operations. For this reason, the SSL
protocol has incorporated an optional session caching scheme protocol has incorporated an optional session caching scheme
to reduce the number of connections that need to be to reduce the number of connections that need to be
established from scratch. Additionally, care has been taken established from scratch. Additionally, care has been taken
to reduce network activity. to reduce network activity.
3. Goals of this document 3. Goals of This Document
The SSL Protocol Version 3.0 Specification is intended primarily for The SSL protocol version 3.0 specification is intended primarily for
readers who will be implementing the protocol and those doing readers who will be implementing the protocol and those doing
cryptographic analysis of it. The spec has been written with this in cryptographic analysis of it. The spec has been written with this in
mind, and it is intended to reflect the needs of those two groups. mind, and it is intended to reflect the needs of those two groups.
For that reason, many of the algorithm-dependent data structures and For that reason, many of the algorithm-dependent data structures and
rules are included in the body of the text (as opposed to in an rules are included in the body of the text (as opposed to in an
Appendix), providing easier access to them. appendix), providing easier access to them.
This document is not intended to supply any details of service This document is not intended to supply any details of service
definition nor interface definition, although it does cover select definition or interface definition, although it does cover select
areas of policy as they are required for the maintenance of solid areas of policy as they are required for the maintenance of solid
security. security.
4. Presentation language 4. Presentation Language
This document deals with the formatting of data in an external This document deals with the formatting of data in an external
representation. The following very basic and somewhat casually representation. The following very basic and somewhat casually
defined presentation syntax will be used. The syntax draws from defined presentation syntax will be used. The syntax draws from
several sources in its structure. Although it resembles the several sources in its structure. Although it resembles the
programming language "C" in its syntax and XDR [RFC1832] in both its programming language "C" in its syntax and External Data
syntax and intent, it would be risky to draw too many parallels. The Representation (XDR) [RFC1832] in both its syntax and intent, it
purpose of this presentation language is to document SSL only, not to would be risky to draw too many parallels. The purpose of this
have general application beyond that particular goal. presentation language is to document SSL only, not to have general
application beyond that particular goal.
4.1. Basic block size 4.1. Basic Block Size
The representation of all data items is explicitly specified. The The representation of all data items is explicitly specified. The
basic data block size is one byte (i.e. 8 bits). Multiple byte data basic data block size is one byte (i.e., 8 bits). Multiple byte data
items are concatenations of bytes, from left to right, from top to items are concatenations of bytes, from left to right, from top to
bottom. From the bytestream a multi-byte item (a numeric in the bottom. From the byte stream, a multi-byte item (a numeric in the
example) is formed (using C notation) by: example) is formed (using C notation) by:
value = (byte[0] << 8*(n-1)) | (byte[1] << 8*(n-2)) | ... value = (byte[0] << 8*(n-1)) | (byte[1] << 8*(n-2)) | ...
| byte[n-1]; | byte[n-1];
This byte ordering for multi-byte values is the commonplace network This byte ordering for multi-byte values is the commonplace network
byte order or big endian format. byte order or big-endian format.
4.2. Miscellaneous 4.2. Miscellaneous
Comments begin with "/*" and end with "*/". Optional components are Comments begin with "/*" and end with "*/". Optional components are
denoted by enclosing them in "[[ ]]" double brackets. Single byte denoted by enclosing them in "[[ ]]" double brackets. Single-byte
entities containing uninterpreted data are of type opaque. entities containing uninterpreted data are of type opaque.
4.3. Vectors 4.3. Vectors
A vector (single dimensioned array) is a stream of homogeneous data A vector (single dimensioned array) is a stream of homogeneous data
elements. The size of the vector may be specified at documentation elements. The size of the vector may be specified at documentation
time or left unspecified until runtime. In either case the length time or left unspecified until runtime. In either case, the length
declares the number of bytes, not the number of elements, in the declares the number of bytes, not the number of elements, in the
vector. The syntax for specifying a new type T' that is a fixed vector. The syntax for specifying a new type T' that is a fixed-
length vector of type T is length vector of type T is
T T'[n]; T T'[n];
Here T' occupies n bytes in the data stream, where n is a multiple of Here, T' occupies n bytes in the data stream, where n is a multiple
the size of T. The length of the vector is not included in the of the size of T. The length of the vector is not included in the
encoded stream. encoded stream.
In the following example, Datum is defined to be three consecutive In the following example, Datum is defined to be three consecutive
bytes that the protocol does not interpret, while Data is three bytes that the protocol does not interpret, while Data is three
consecutive Datum, consuming a total of nine bytes. consecutive Datum, consuming a total of nine bytes.
opaque Datum[3]; /* three uninterpreted bytes */ opaque Datum[3]; /* three uninterpreted bytes */
Datum Data[9]; /* 3 consecutive 3 byte vectors */ Datum Data[9]; /* 3 consecutive 3 byte vectors */
Variable length vectors are defined by specifying a subrange of legal Variable-length vectors are defined by specifying a subrange of legal
lengths, inclusively, using the notation <floor..ceiling>. When lengths, inclusively, using the notation <floor..ceiling>. When
encoded, the actual length precedes the vector's contents in the byte encoded, the actual length precedes the vector's contents in the byte
stream. The length will be in the form of a number consuming as many stream. The length will be in the form of a number consuming as many
bytes as required to hold the vector's specified maximum (ceiling) bytes as required to hold the vector's specified maximum (ceiling)
length. A variable length vector with an actual length field of zero length. A variable-length vector with an actual length field of zero
is referred to as an empty vector. is referred to as an empty vector.
T T'<floor..ceiling>; T T'<floor..ceiling>;
In the following example, mandatory is a vector that must contain In the following example, mandatory is a vector that must contain
between 300 and 400 bytes of type opaque. It can never be empty. between 300 and 400 bytes of type opaque. It can never be empty.
The actual length field consumes two bytes, a uint16, sufficient to The actual length field consumes two bytes, a uint16, sufficient to
represent the value 400 (see Section 4.4). On the other hand, longer represent the value 400 (see Section 4.4). On the other hand, longer
can represent up to 800 bytes of data, or 400 uint16 elements, and it can represent up to 800 bytes of data, or 400 uint16 elements, and it
may be empty. Its encoding will include a two byte actual length may be empty. Its encoding will include a two-byte actual length
field prepended to the vector. field prepended to the vector.
opaque mandatory<300..400>; opaque mandatory<300..400>;
/* length field is 2 bytes, cannot be empty */ /* length field is 2 bytes, cannot be empty */
uint16 longer<0..800>; uint16 longer<0..800>;
/* zero to 400 16-bit unsigned integers */ /* zero to 400 16-bit unsigned integers */
4.4. Numbers 4.4. Numbers
The basic numeric data type is an unsigned byte (uint8). All larger The basic numeric data type is an unsigned byte (uint8). All larger
numeric data types are formed from fixed length series of bytes numeric data types are formed from fixed-length series of bytes
concatenated as described in Section 4.1 and are also unsigned. The concatenated as described in Section 4.1 and are also unsigned. The
following numeric types are predefined. following numeric types are predefined.
uint8 uint16[2]; uint8 uint16[2];
uint8 uint24[3]; uint8 uint24[3];
uint8 uint32[4]; uint8 uint32[4];
uint8 uint64[8]; uint8 uint64[8];
4.5. Enumerateds 4.5. Enumerateds
skipping to change at page 9, line 5 skipping to change at page 9, line 11
assigned any unique value, in any order. assigned any unique value, in any order.
enum { e1(v1), e2(v2), ... , en(vn), [[(n)]] } Te; enum { e1(v1), e2(v2), ... , en(vn), [[(n)]] } Te;
Enumerateds occupy as much space in the byte stream as would its Enumerateds occupy as much space in the byte stream as would its
maximal defined ordinal value. The following definition would cause maximal defined ordinal value. The following definition would cause
one byte to be used to carry fields of type Color. one byte to be used to carry fields of type Color.
enum { red(3), blue(5), white(7) } Color; enum { red(3), blue(5), white(7) } Color;
One may optionally specify a value without its associated tag to Optionally, one may specify a value without its associated tag to
force the width definition without defining a superfluous element. force the width definition without defining a superfluous element.
In the following example, Taste will consume two bytes in the data In the following example, Taste will consume two bytes in the data
stream but can only assume the values 1, 2 or 4. stream but can only assume the values 1, 2, or 4.
enum { sweet(1), sour(2), bitter(4), (32000) } Taste; enum { sweet(1), sour(2), bitter(4), (32000) } Taste;
The names of the elements of an enumeration are scoped within the The names of the elements of an enumeration are scoped within the
defined type. In the first example, a fully qualified reference to defined type. In the first example, a fully qualified reference to
the second element of the enumeration would be Color.blue. Such the second element of the enumeration would be Color.blue. Such
qualification is not required if the target of the assignment is well qualification is not required if the target of the assignment is well
specified. specified.
Color color = Color.blue; /* overspecified, legal */ Color color = Color.blue; /* overspecified, legal */
Color color = blue; /* correct, type implicit */ Color color = blue; /* correct, type implicit */
For enumerateds that are never converted to external representation, For enumerateds that are never converted to external representation,
the numerical information may be omitted. the numerical information may be omitted.
enum { low, medium, high } Amount; enum { low, medium, high } Amount;
4.6. Constructed types 4.6. Constructed Types
Structure types may be constructed from primitive types for Structure types may be constructed from primitive types for
convenience. Each specification declares a new, unique type. The convenience. Each specification declares a new, unique type. The
syntax for definition is much like that of C. syntax for definition is much like that of C.
struct { struct {
T1 f1; T1 f1;
T2 f2; T2 f2;
... ...
Tn fn; Tn fn;
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.... ....
Tn fn; Tn fn;
select (E) { select (E) {
case e1: Te1; case e1: Te1;
case e2: Te2; case e2: Te2;
.... ....
case en: Ten; case en: Ten;
} [[fv]]; } [[fv]];
} [[Tv]]; } [[Tv]];
For example For example,
enum { apple, orange } VariantTag; enum { apple, orange } VariantTag;
struct { struct {
uint16 number; uint16 number;
opaque string<0..10>; /* variable length */ opaque string<0..10>; /* variable length */
} V1; } V1;
struct { struct {
uint32 number; uint32 number;
opaque string[10]; /* fixed length */ opaque string[10]; /* fixed length */
} V2; } V2;
struct { struct {
select (VariantTag) { /* value of selector is implicit */ select (VariantTag) { /* value of selector is implicit */
case apple: V1; /* VariantBody, tag = apple */ case apple: V1; /* VariantBody, tag = apple */
case orange: V2; /* VariantBody, tag = orange */ case orange: V2; /* VariantBody, tag = orange */
} variant_body; /* optional label on variant */ } variant_body; /* optional label on variant */
} VariantRecord; } VariantRecord;
Variant structures may be qualified (narrowed) by specifying a value Variant structures may be qualified (narrowed) by specifying a value
for the selector prior to the type. For example, a for the selector prior to the type. For example, an
orange VariantRecord orange VariantRecord
is a narrowed type of a VariantRecord containing a variant_body of is a narrowed type of a VariantRecord containing a variant_body of
type V2. type V2.
4.7. Cryptographic attributes 4.7. Cryptographic Attributes
The four cryptographic operations digital signing, stream cipher The four cryptographic operations digital signing, stream cipher
encryption, block cipher encryption, and public key encryption are encryption, block cipher encryption, and public key encryption are
designated digitally-signed, stream-ciphered, block-ciphered, and designated digitally-signed, stream-ciphered, block-ciphered, and
public-key-encrypted, respectively. A field's cryptographic public-key-encrypted, respectively. A field's cryptographic
processing is specified by prepending an appropriate key word processing is specified by prepending an appropriate key word
designation before the field's type specification. Cryptographic designation before the field's type specification. Cryptographic
keys are implied by the current session state (see Section 5.1). keys are implied by the current session state (see Section 5.1).
In digital signing, one-way hash functions are used as input for a In digital signing, one-way hash functions are used as input for a
signing algorithm. In RSA signing, a 36-byte structure of two hashes signing algorithm. In RSA signing, a 36-byte structure of two hashes
(one SHA and one MD5) is signed (encrypted with the private key). In (one SHA and one MD5) is signed (encrypted with the private key). In
DSS, the 20 bytes of the SHA hash are run directly through the DSS, the 20 bytes of the SHA hash are run directly through the
Digital Signing Algorithm with no additional hashing. Digital Signature Algorithm with no additional hashing.
In stream cipher encryption, the plaintext is exclusive-ORed with an In stream cipher encryption, the plaintext is exclusive-ORed with an
identical amount of output generated from a cryptographically-secure identical amount of output generated from a cryptographically secure
keyed pseudorandom number generator. keyed pseudorandom number generator.
In block cipher encryption, every block of plaintext encrypts to a In block cipher encryption, every block of plaintext encrypts to a
block of ciphertext. Because it is unlikely that the plaintext block of ciphertext. Because it is unlikely that the plaintext
(whatever data is to be sent) will break neatly into the necessary (whatever data is to be sent) will break neatly into the necessary
block size (usually 64 bits), it is necessary to pad out the end of block size (usually 64 bits), it is necessary to pad out the end of
short blocks with some regular pattern, usually all zeroes. short blocks with some regular pattern, usually all zeroes.
In public key encryption, one-way functions with secret "trapdoors" In public key encryption, one-way functions with secret "trapdoors"
are used to encrypt the outgoing data. Data encrypted with the are used to encrypt the outgoing data. Data encrypted with the
public key of a given key pair can only be decrypted with the private public key of a given key pair can only be decrypted with the private
key, and vice-versa. In the following example: key, and vice versa. In the following example:
stream-ciphered struct { stream-ciphered struct {
uint8 field1; uint8 field1;
uint8 field2; uint8 field2;
digitally-signed opaque hash[20]; digitally-signed opaque hash[20];
} UserType; } UserType;
The contents of hash are used as input for the signing algorithm, The contents of hash are used as input for the signing algorithm,
then the entire structure is encrypted with a stream cipher. then the entire structure is encrypted with a stream cipher.
4.8. Constants 4.8. Constants
Typed constants can be defined for purposes of specification by Typed constants can be defined for purposes of specification by
declaring a symbol of the desired type and assigning values to it. declaring a symbol of the desired type and assigning values to it.
Under-specified types (opaque, variable length vectors, and Under-specified types (opaque, variable-length vectors, and
structures that contain opaque) cannot be assigned values. No fields structures that contain opaque) cannot be assigned values. No fields
of a multi-element structure or vector may be elided. of a multi-element structure or vector may be elided.
For example, For example,
struct { struct {
uint8 f1; uint8 f1;
uint8 f2; uint8 f2;
} Example1; } Example1;
Example1 ex1 = {1, 4};/* assigns f1 = 1, f2 = 4 */ Example1 ex1 = {1, 4};/* assigns f1 = 1, f2 = 4 */
5. SSL protocol 5. SSL Protocol
SSL is a layered protocol. At each layer, messages may include SSL is a layered protocol. At each layer, messages may include
fields for length, description, and content. SSL takes messages to fields for length, description, and content. SSL takes messages to
be transmitted, fragments the data into manageable blocks, optionally be transmitted, fragments the data into manageable blocks, optionally
compresses the data, applies a MAC, encrypts, and transmits the compresses the data, applies a MAC, encrypts, and transmits the
result. Received data is decrypted, verified, decompressed, and result. Received data is decrypted, verified, decompressed, and
reassembled, then delivered to higher level clients. reassembled, then delivered to higher level clients.
5.1. Session and connection states 5.1. Session and Connection States
An SSL session is stateful. It is the responsibility of the SSL An SSL session is stateful. It is the responsibility of the SSL
Handshake protocol to coordinate the states of the client and server, handshake protocol to coordinate the states of the client and server,
thereby allowing the protocol state machines of each to operate thereby allowing the protocol state machines of each to operate
consistently, despite the fact that the state is not exactly consistently, despite the fact that the state is not exactly
parallel. Logically the state is represented twice, once as the parallel. Logically, the state is represented twice, once as the
current operating state, and (during the handshake protocol) again as current operating state and (during the handshake protocol) again as
the pending state. Additionally, separate read and write states are the pending state. Additionally, separate read and write states are
maintained. When the client or server receives a change cipher spec maintained. When the client or server receives a change cipher spec
message, it copies the pending read state into the current read message, it copies the pending read state into the current read
state. When the client or server sends a change cipher spec message, state. When the client or server sends a change cipher spec message,
it copies the pending write state into the current write state. When it copies the pending write state into the current write state. When
the handshake negotiation is complete, the client and server exchange the handshake negotiation is complete, the client and server exchange
change cipher spec messages (see Section 5.3), and they then change cipher spec messages (see Section 5.3), and they then
communicate using the newly agreed-upon cipher spec. communicate using the newly agreed-upon cipher spec.
An SSL session may include multiple secure connections; in addition, An SSL session may include multiple secure connections; in addition,
parties may have multiple simultaneous sessions. parties may have multiple simultaneous sessions.
The session state includes the following elements: The session state includes the following elements:
session identifier An arbitrary byte sequence chosen by the server session identifier: An arbitrary byte sequence chosen by the server
to identify an active or resumable session state. to identify an active or resumable session state.
peer certificate X509.v3[X509] certificate of the peer. This peer certificate: X509.v3 [X509] certificate of the peer. This
element of the state may be null. element of the state may be null.
compression method The algorithm used to compress data prior to compression method: The algorithm used to compress data prior to
encryption. encryption.
cipher spec Specifies the bulk data encryption algorithm (such as cipher spec: Specifies the bulk data encryption algorithm (such as
null, DES, etc.) and a MAC algorithm (such as MD5 or SHA). It null, DES, etc.) and a MAC algorithm (such as MD5 or SHA). It
also defines cryptographic attributes such as the hash_size. (See also defines cryptographic attributes such as the hash_size. (See
Appendix A.7 for formal definition) Appendix A.7 for formal definition.)
master secret 48-byte secret shared between the client and server. master secret: 48-byte secret shared between the client and server.
is resumable A flag indicating whether the session can be used to is resumable: A flag indicating whether the session can be used to
initiate new connections. initiate new connections.
The connection state includes the following elements: The connection state includes the following elements:
server and client random Byte sequences that are chosen by the server and client random: Byte sequences that are chosen by the
server and client for each connection. server and client for each connection.
server write MAC secret The secret used in MAC operations on data server write MAC secret: The secret used in MAC operations on data
written by the server written by the server.
client write MAC secret The secret used in MAC operations on data client write MAC secret: The secret used in MAC operations on data
written by the client. written by the client.
server write key The bulk cipher key for data encrypted by the server write key: The bulk cipher key for data encrypted by the
server and decrypted by the client. server and decrypted by the client.
client write key The bulk cipher key for data encrypted by the client write key: The bulk cipher key for data encrypted by the
client and decrypted by the server. client and decrypted by the server.
initialization vectors When a block cipher in CBC mode is used, an initialization vectors: When a block cipher in Cipher Block Chaining
initialization vector (IV) is maintained for each key. This field (CBC) mode is used, an initialization vector (IV) is maintained
is first initialized by the SSL handshake protocol. Thereafter for each key. This field is first initialized by the SSL
the final ciphertext block from each record is preserved for use handshake protocol. Thereafter, the final ciphertext block from
with the following record. each record is preserved for use with the following record.
sequence numbers Each party maintains separate sequence numbers for sequence numbers: Each party maintains separate sequence numbers for
transmitted and received messages for each connection. When a transmitted and received messages for each connection. When a
party sends or receives a change cipher spec message, the party sends or receives a change cipher spec message, the
appropriate sequence number is set to zero. Sequence numbers are appropriate sequence number is set to zero. Sequence numbers are
of type uint64 and may not exceed 2^64-1. of type uint64 and may not exceed 2^64-1.
5.2. Record layer 5.2. Record Layer
The SSL Record Layer receives uninterpreted data from higher layers The SSL record layer receives uninterpreted data from higher layers
in non-empty blocks of arbitrary size. in non-empty blocks of arbitrary size.
5.2.1. Fragmentation 5.2.1. Fragmentation
The record layer fragments information blocks into SSLPlaintext The record layer fragments information blocks into SSLPlaintext
records of 2^14 bytes or less. Client message boundaries are not records of 2^14 bytes or less. Client message boundaries are not
preserved in the record layer (i.e., multiple client messages of the preserved in the record layer (i.e., multiple client messages of the
same ContentType may be coalesced into a single SSLPlaintext record). same ContentType may be coalesced into a single SSLPlaintext record).
struct { struct {
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application_data(23), (255) application_data(23), (255)
} ContentType; } ContentType;
struct { struct {
ContentType type; ContentType type;
ProtocolVersion version; ProtocolVersion version;
uint16 length; uint16 length;
opaque fragment[SSLPlaintext.length]; opaque fragment[SSLPlaintext.length];
} SSLPlaintext; } SSLPlaintext;
type The higher level protocol used to process the enclosed type: The higher level protocol used to process the enclosed
fragment. fragment.
version The version of protocol being employed. This document version: The version of protocol being employed. This document
describes SSL Version 3.0 (See Appendix A.1). describes SSL version 3.0 (see Appendix A.1).
length The length (in bytes) of the following SSLPlaintext.fragment. length: The length (in bytes) of the following
The length should not exceed 2^14. SSLPlaintext.fragment. The length should not exceed 2^14.
fragment The application data. This data is transparent and treated fragment: The application data. This data is transparent and
as an independent block to be dealt with by the higher level treated as an independent block to be dealt with by the higher
protocol specified by the type field. level protocol specified by the type field.
Note: Data of different SSL Record layer content types may be Note: Data of different SSL record layer content types may be
interleaved. Application data is generally of lower precedence for interleaved. Application data is generally of lower precedence for
transmission than other content types. transmission than other content types.
5.2.2. Record compression and decompression 5.2.2. Record Compression and Decompression
All records are compressed using the compression algorithm defined in All records are compressed using the compression algorithm defined in
the current session state. There is always an active compression the current session state. There is always an active compression
algorithm, however initially it is defined as CompressionMethod.null. algorithm; however, initially it is defined as
The compression algorithm translates an SSLPlaintext structure into CompressionMethod.null. The compression algorithm translates an
an SSLCompressed structure. Compression functions erase their state SSLPlaintext structure into an SSLCompressed structure. Compression
information whenever the CipherSpec is replaced. functions erase their state information whenever the CipherSpec is
replaced.
Note: The CipherSpec is part of the session state described in Note: The CipherSpec is part of the session state described in
Section 5.1. References to fields of the CipherSpec are made Section 5.1. References to fields of the CipherSpec are made
throughout this document using presentation syntax. A more complete throughout this document using presentation syntax. A more complete
description of the CipherSpec is shown in Appendix A.7. description of the CipherSpec is shown in Appendix A.7.
Compression must be lossless and may not increase the content length Compression must be lossless and may not increase the content length
by more than 1024 bytes. If the decompression function encounters an by more than 1024 bytes. If the decompression function encounters an
SSLCompressed.fragment that would decompress to a length in excess of SSLCompressed.fragment that would decompress to a length in excess of
2^14 bytes, it should issue a fatal decompression_failure alert 2^14 bytes, it should issue a fatal decompression_failure alert
(Section 5.4.2). (Section 5.4.2).
struct { struct {
ContentType type; /* same as SSLPlaintext.type */ ContentType type; /* same as SSLPlaintext.type */
ProtocolVersion version;/* same as SSLPlaintext.version */ ProtocolVersion version;/* same as SSLPlaintext.version */
uint16 length; uint16 length;
opaque fragment[SSLCompressed.length]; opaque fragment[SSLCompressed.length];
} SSLCompressed; } SSLCompressed;
length The length (in bytes) of the following length: The length (in bytes) of the following
SSLCompressed.fragment. The length should not exceed 2^14 + 1024. SSLCompressed.fragment. The length should not exceed 2^14 + 1024.
fragment The compressed form of SSLPlaintext.fragment. fragment: The compressed form of SSLPlaintext.fragment.
Note: A CompressionMethod.null operation is an identity operation; no Note: A CompressionMethod.null operation is an identity operation; no
fields are altered. (See Appendix A.4.1) fields are altered (see Appendix A.4.1.)
Implementation note: Decompression functions are responsible for Implementation note: Decompression functions are responsible for
ensuring that messages cannot cause internal buffer overflows. ensuring that messages cannot cause internal buffer overflows.
5.2.3. Record payload protection and the CipherSpec 5.2.3. Record Payload Protection and the CipherSpec
All records are protected using the encryption and MAC algorithms All records are protected using the encryption and MAC algorithms
defined in the current CipherSpec. There is always an active defined in the current CipherSpec. There is always an active
CipherSpec, however initially it is SSL_NULL_WITH_NULL_NULL, which CipherSpec; however, initially it is SSL_NULL_WITH_NULL_NULL, which
does not provide any security. does not provide any security.
Once the handshake is complete, the two parties have shared secrets Once the handshake is complete, the two parties have shared secrets
which are used to encrypt records and compute keyed message that are used to encrypt records and compute keyed Message
authentication codes (MACs) on their contents. The techniques used Authentication Codes (MACs) on their contents. The techniques used
to perform the encryption and MAC operations are defined by the to perform the encryption and MAC operations are defined by the
CipherSpec and constrained by CipherSpec.cipher_type. The encryption CipherSpec and constrained by CipherSpec.cipher_type. The encryption
and MAC functions translate an SSLCompressed structure into an and MAC functions translate an SSLCompressed structure into an
SSLCiphertext. The decryption functions reverse the process. SSLCiphertext. The decryption functions reverse the process.
Transmissions also include a sequence number so that missing, Transmissions also include a sequence number so that missing,
altered, or extra messages are detectable. altered, or extra messages are detectable.
struct { struct {
ContentType type; ContentType type;
ProtocolVersion version; ProtocolVersion version;
uint16 length; uint16 length;
select (CipherSpec.cipher_type) { select (CipherSpec.cipher_type) {
case stream: GenericStreamCipher; case stream: GenericStreamCipher;
case block: GenericBlockCipher; case block: GenericBlockCipher;
} fragment; } fragment;
} SSLCiphertext; } SSLCiphertext;
type The type field is identical to SSLCompressed.type. type: The type field is identical to SSLCompressed.type.
version The version field is identical to SSLCompressed.version. version: The version field is identical to SSLCompressed.version.
length The length (in bytes) of the following length: The length (in bytes) of the following
SSLCiphertext.fragment. The length may not exceed 2^14 + 2048. SSLCiphertext.fragment. The length may not exceed 2^14 + 2048.
fragment The encrypted form of SSLCompressed.fragment, including the fragment: The encrypted form of SSLCompressed.fragment, including
MAC. the MAC.
5.2.3.1. Null or standard stream cipher 5.2.3.1. Null or Standard Stream Cipher
Stream ciphers (including BulkCipherAlgorithm.null - see Appendix Stream ciphers (including BulkCipherAlgorithm.null; see Appendix A.7)
A.7) convert SSLCompressed.fragment structures to and from stream convert SSLCompressed.fragment structures to and from stream
SSLCiphertext.fragment structures. SSLCiphertext.fragment structures.
stream-ciphered struct { stream-ciphered struct {
opaque content[SSLCompressed.length]; opaque content[SSLCompressed.length];
opaque MAC[CipherSpec.hash_size]; opaque MAC[CipherSpec.hash_size];
} GenericStreamCipher; } GenericStreamCipher;
The MAC is generated as: The MAC is generated as:
hash(MAC_write_secret + pad_2 + hash(MAC_write_secret + pad_2 +
hash(MAC_write_secret + pad_1 + seq_num + hash(MAC_write_secret + pad_1 + seq_num +
SSLCompressed.type + SSLCompressed.length + SSLCompressed.type + SSLCompressed.length +
SSLCompressed.fragment)); SSLCompressed.fragment));
where "+" denotes concatenation. where "+" denotes concatenation.
pad_1 The character 0x36 repeated 48 times for MD5 or 40 times for pad_1: The character 0x36 repeated 48 times for MD5 or 40 times for
SHA. SHA.
pad_2 The character 0x5c repeated 48 times for MD5 or 40 times for pad_2: The character 0x5c repeated 48 times for MD5 or 40 times for
SHA. SHA.
seq_num The sequence number for this message. seq_num: The sequence number for this message.
hash Hashing algorithm derived from the cipher suite. hash: Hashing algorithm derived from the cipher suite.
Note that the MAC is computed before encryption. The stream cipher Note that the MAC is computed before encryption. The stream cipher
encrypts the entire block, including the MAC. For stream ciphers encrypts the entire block, including the MAC. For stream ciphers
that do not use a synchronization vector (such as RC4), the stream that do not use a synchronization vector (such as RC4), the stream
cipher state from the end of one record is simply used on the cipher state from the end of one record is simply used on the
subsequent packet. If the CipherSuite is SSL_NULL_WITH_NULL_NULL, subsequent packet. If the CipherSuite is SSL_NULL_WITH_NULL_NULL,
encryption consists of the identity operation (i.e., the data is not encryption consists of the identity operation (i.e., the data is not
encrypted and the MAC size is zero implying that no MAC is used). encrypted and the MAC size is zero implying that no MAC is used).
SSLCiphertext.length is SSLCompressed.length plus SSLCiphertext.length is SSLCompressed.length plus
CipherSpec.hash_size. CipherSpec.hash_size.
5.2.3.2. CBC block cipher 5.2.3.2. CBC Block Cipher
For block ciphers (such as RC2 or DES), the encryption and MAC For block ciphers (such as RC2 or DES), the encryption and MAC
functions convert SSLCompressed.fragment structures to and from block functions convert SSLCompressed.fragment structures to and from block
SSLCiphertext.fragment structures. SSLCiphertext.fragment structures.
block-ciphered struct { block-ciphered struct {
opaque content[SSLCompressed.length]; opaque content[SSLCompressed.length];
opaque MAC[CipherSpec.hash_size]; opaque MAC[CipherSpec.hash_size];
uint8 padding[GenericBlockCipher.padding_length]; uint8 padding[GenericBlockCipher.padding_length];
uint8 padding_length; uint8 padding_length;
} GenericBlockCipher; } GenericBlockCipher;
The MAC is generated as described in Section 5.2.3.1. The MAC is generated as described in Section 5.2.3.1.
padding Padding that is added to force the length of the plaintext padding: Padding that is added to force the length of the plaintext
to be a multiple of the block cipher's block length. to be a multiple of the block cipher's block length.
padding_length The length of the padding must be less than the padding_length: The length of the padding must be less than the
cipher's block length and may be zero. The padding length should cipher's block length and may be zero. The padding length should
be such that the total size of the GenericBlockCipher structure is be such that the total size of the GenericBlockCipher structure is
a multiple of the cipher's block length. a multiple of the cipher's block length.
The encrypted data length (SSLCiphertext.length) is one more than the The encrypted data length (SSLCiphertext.length) is one more than the
sum of SSLCompressed.length, CipherSpec.hash_size, and sum of SSLCompressed.length, CipherSpec.hash_size, and
padding_length. padding_length.
Note: With CBC block chaining the initialization vector (IV) for the Note: With CBC, the initialization vector (IV) for the first record
first record is provided by the handshake protocol. The IV for is provided by the handshake protocol. The IV for subsequent records
subsequent records is the last ciphertext block from the previous is the last ciphertext block from the previous record.
record.
5.3. Change cipher spec protocol 5.3. Change Cipher Spec Protocol
The change cipher spec protocol exists to signal transitions in The change cipher spec protocol exists to signal transitions in
ciphering strategies. The protocol consists of a single message, ciphering strategies. The protocol consists of a single message,
which is encrypted and compressed under the current (not the pending) which is encrypted and compressed under the current (not the pending)
CipherSpec. The message consists of a single byte of value 1. CipherSpec. The message consists of a single byte of value 1.
struct { struct {
enum { change_cipher_spec(1), (255) } type; enum { change_cipher_spec(1), (255) } type;
} ChangeCipherSpec; } ChangeCipherSpec;
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of this message causes the receiver to copy the read pending state of this message causes the receiver to copy the read pending state
into the read current state. The client sends a change cipher spec into the read current state. The client sends a change cipher spec
message following handshake key exchange and certificate verify message following handshake key exchange and certificate verify
messages (if any), and the server sends one after successfully messages (if any), and the server sends one after successfully
processing the key exchange message it received from the client. An processing the key exchange message it received from the client. An
unexpected change cipher spec message should generate an unexpected change cipher spec message should generate an
unexpected_message alert (Section 5.4.2). When resuming a previous unexpected_message alert (Section 5.4.2). When resuming a previous
session, the change cipher spec message is sent after the hello session, the change cipher spec message is sent after the hello
messages. messages.
5.4. Alert protocol 5.4. Alert Protocol
One of the content types supported by the SSL Record layer is the One of the content types supported by the SSL record layer is the
alert type. Alert messages convey the severity of the message and a alert type. Alert messages convey the severity of the message and a
description of the alert. Alert messages with a level of fatal description of the alert. Alert messages with a level of fatal
result in the immediate termination of the connection. In this case, result in the immediate termination of the connection. In this case,
other connections corresponding to the session may continue, but the other connections corresponding to the session may continue, but the
session identifier must be invalidated, preventing the failed session session identifier must be invalidated, preventing the failed session
from being used to establish new connections. Like other messages, from being used to establish new connections. Like other messages,
alert messages are encrypted and compressed, as specified by the alert messages are encrypted and compressed, as specified by the
current connection state. current connection state.
enum { warning(1), fatal(2), (255) } AlertLevel; enum { warning(1), fatal(2), (255) } AlertLevel;
skipping to change at page 19, line 28 skipping to change at page 19, line 28
certificate_unknown(46), certificate_unknown(46),
illegal_parameter (47) illegal_parameter (47)
(255) (255)
} AlertDescription; } AlertDescription;
struct { struct {
AlertLevel level; AlertLevel level;
AlertDescription description; AlertDescription description;
} Alert; } Alert;
5.4.1. Closure alerts 5.4.1. Closure Alerts
The client and the server must share knowledge that the connection is The client and the server must share knowledge that the connection is
ending in order to avoid a truncation attack. Either party may ending in order to avoid a truncation attack. Either party may
initiate the exchange of closing messages. initiate the exchange of closing messages.
close_notify This message notifies the recipient that the sender close_notify: This message notifies the recipient that the sender
will not send any more messages on this connection. The session will not send any more messages on this connection. The session
becomes unresumable if any connection is terminated without proper becomes unresumable if any connection is terminated without proper
close_notify messages with level equal to warning. close_notify messages with level equal to warning.
Either party may initiate a close by sending a close_notify alert. Either party may initiate a close by sending a close_notify alert.
Any data received after a closure alert is ignored. Any data received after a closure alert is ignored.
Each party is required to send a close_notify alert before closing Each party is required to send a close_notify alert before closing
the write side of the connection. It is required that the other the write side of the connection. It is required that the other
party respond with a close_notify alert of its own and close down the party respond with a close_notify alert of its own and close down the
connection immediately, discarding any pending writes. It is not connection immediately, discarding any pending writes. It is not
required for the initiator of the close to wait for the responding required for the initiator of the close to wait for the responding
close_notify alert before closing the read side of the connection. close_notify alert before closing the read side of the connection.
NB: It is assumed that closing a connection reliably delivers pending NB: It is assumed that closing a connection reliably delivers pending
data before destroying the transport. data before destroying the transport.
5.4.2. Error alerts 5.4.2. Error Alerts
Error handling in the SSL Handshake protocol is very simple. When an Error handling in the SSL handshake protocol is very simple. When an
error is detected, the detecting party sends a message to the other error is detected, the detecting party sends a message to the other
party. Upon transmission or receipt of an fatal alert message, both party. Upon transmission or receipt of a fatal alert message, both
parties immediately close the connection. Servers and clients are parties immediately close the connection. Servers and clients are
required to forget any session-identifiers, keys, and secrets required to forget any session identifiers, keys, and secrets
associated with a failed connection. The following error alerts are associated with a failed connection. The following error alerts are
defined: defined:
unexpected_message An inappropriate message was received. This unexpected_message: An inappropriate message was received. This
alert is always fatal and should never be observed in alert is always fatal and should never be observed in
communication between proper implementations. communication between proper implementations.
bad_record_mac This alert is returned if a record is received with bad_record_mac: This alert is returned if a record is received with
an incorrect MAC. This message is always fatal. an incorrect MAC. This message is always fatal.
decompression_failure The decompression function received improper decompression_failure: The decompression function received improper
input (e.g. data that would expand to excessive length). This input (e.g., data that would expand to excessive length). This
message is always fatal. message is always fatal.
handshake_failure Reception of a handshake_failure alert message handshake_failure: Reception of a handshake_failure alert message
indicates that the sender was unable to negotiate an acceptable indicates that the sender was unable to negotiate an acceptable
set of security parameters given the options available. This is a set of security parameters given the options available. This is a
fatal error. fatal error.
no_certificate A no_certificate alert message may be sent in no_certificate: A no_certificate alert message may be sent in
response to a certification request if no appropriate certificate response to a certification request if no appropriate certificate
is available. is available.
bad_certificate A certificate was corrupt, contained signatures that bad_certificate: A certificate was corrupt, contained signatures
did not verify correctly, etc. that did not verify correctly, etc.
unsupported_certificate A certificate was of an unsupported type. unsupported_certificate: A certificate was of an unsupported type.
certificate_revoked A certificate was revoked by its signer. certificate_revoked: A certificate was revoked by its signer.
certificate_expired A certificate has expired or is not currently certificate_expired: A certificate has expired or is not currently
valid. valid.
certificate_unknown Some other (unspecified) issue arose in certificate_unknown: Some other (unspecified) issue arose in
processing the certificate, rendering it unacceptable. processing the certificate, rendering it unacceptable.
illegal_parameter A field in the handshake was out of range or illegal_parameter: A field in the handshake was out of range or
inconsistent with other fields. This is always fatal. inconsistent with other fields. This is always fatal.
5.5. Handshake protocol overview 5.5. Handshake Protocol Overview
The cryptographic parameters of the session state are produced by the The cryptographic parameters of the session state are produced by the
SSL Handshake Protocol, which operates on top of the SSL Record SSL handshake protocol, which operates on top of the SSL record
Layer. When a SSL client and server first start communicating, they layer. When an SSL client and server first start communicating, they
agree on a protocol version, select cryptographic algorithms, agree on a protocol version, select cryptographic algorithms,
optionally authenticate each other, and use public-key encryption optionally authenticate each other, and use public key encryption
techniques to generate shared secrets. These processes are performed techniques to generate shared secrets. These processes are performed
in the handshake protocol, which can be summarized as follows: The in the handshake protocol, which can be summarized as follows: the
client sends a client hello message to which the server must respond client sends a client hello message to which the server must respond
with a server hello message, or else a fatal error will occur and the with a server hello message, or else a fatal error will occur and the
connection will fail. The client hello and server hello are used to connection will fail. The client hello and server hello are used to
establish security enhancement capabilities between client and establish security enhancement capabilities between client and
server. The client hello and server hello establish the following server. The client hello and server hello establish the following
attributes: Protocol Version, Session ID, Cipher Suite, and attributes: Protocol Version, Session ID, Cipher Suite, and
Compression Method. Additionally, two random values are generated Compression Method. Additionally, two random values are generated
and exchanged: ClientHello.random and ServerHello.random. and exchanged: ClientHello.random and ServerHello.random.
Following the hello messages, the server will send its certificate, Following the hello messages, the server will send its certificate,
if it is to be authenticated. Additionally, a server key exchange if it is to be authenticated. Additionally, a server key exchange
message may be sent, if it is required (e.g. if their server has no message may be sent, if it is required (e.g., if their server has no
certificate, or if its certificate is for signing only). If the certificate, or if its certificate is for signing only). If the
server is authenticated, it may request a certificate from the server is authenticated, it may request a certificate from the
client, if that is appropriate to the cipher suite selected. Now the client, if that is appropriate to the cipher suite selected. Now the
server will send the server hello done message, indicating that the server will send the server hello done message, indicating that the
hello-message phase of the handshake is complete. The server will hello-message phase of the handshake is complete. The server will
then wait for a client response. If the server has sent a then wait for a client response. If the server has sent a
certificate request Message, the client must send either the certificate request message, the client must send either the
certificate message or a no_certificate alert. The client key certificate message or a no_certificate alert. The client key
exchange message is now sent, and the content of that message will exchange message is now sent, and the content of that message will
depend on the public key algorithm selected between the client hello depend on the public key algorithm selected between the client hello
and the server hello. If the client has sent a certificate with and the server hello. If the client has sent a certificate with
signing ability, a digitally-signed certificate verify message is signing ability, a digitally-signed certificate verify message is
sent to explicitly verify the certificate. sent to explicitly verify the certificate.
At this point, a change cipher spec message is sent by the client, At this point, a change cipher spec message is sent by the client,
and the client copies the pending Cipher Spec into the current Cipher and the client copies the pending CipherSpec into the current
Spec. The client then immediately sends the finished message under CipherSpec. The client then immediately sends the finished message
the new algorithms, keys, and secrets. In response, the server will under the new algorithms, keys, and secrets. In response, the server
send its own change cipher spec message, transfer the pending to the will send its own change cipher spec message, transfer the pending to
current Cipher Spec, and send its finished message under the new the current CipherSpec, and send its finished message under the new
Cipher Spec. At this point, the handshake is complete and the client CipherSpec. At this point, the handshake is complete and the client
and server may begin to exchange application layer data. (See flow and server may begin to exchange application layer data. (See flow
chart below.) chart below.)
Client Server Client Server
ClientHello --------> ClientHello -------->
ServerHello ServerHello
Certificate* Certificate*
ServerKeyExchange* ServerKeyExchange*
CertificateRequest* CertificateRequest*
<-------- ServerHelloDone <-------- ServerHelloDone
Certificate* Certificate*
ClientKeyExchange ClientKeyExchange
CertificateVerify* CertificateVerify*
[ChangeCipherSpec] [ChangeCipherSpec]
Finished --------> Finished -------->
[ChangeCipherSpec] [ChangeCipherSpec]
<-------- Finished <-------- Finished
Application Data <-------> Application Data Application Data <-------> Application Data
* Indicates optional or situation-dependent messages that are not * Indicates optional or situation-dependent messages that are not
always sent. always sent.
Note: To help avoid pipeline stalls, ChangeCipherSpec is an Note: To help avoid pipeline stalls, ChangeCipherSpec is an
independent SSL Protocol content type, and is not actually an SSL independent SSL protocol content type, and is not actually an SSL
handshake message. handshake message.
When the client and server decide to resume a previous session or When the client and server decide to resume a previous session or
duplicate an existing session (instead of negotiating new security duplicate an existing session (instead of negotiating new security
parameters) the message flow is as follows: parameters) the message flow is as follows:
The client sends a ClientHello using the Session ID of the session to The client sends a ClientHello using the session ID of the session to
be resumed. The server then checks its session cache for a match. be resumed. The server then checks its session cache for a match.
If a match is found, and the server is willing to re-establish the If a match is found, and the server is willing to re-establish the
connection under the specified session state, it will send a connection under the specified session state, it will send a
ServerHello with the same Session ID value. At this point, both ServerHello with the same session ID value. At this point, both
client and server must send change cipher spec messages and proceed client and server must send change cipher spec messages and proceed
directly to finished messages. Once the re-establishment is directly to finished messages. Once the re-establishment is
complete, the client and server may begin to exchange application complete, the client and server may begin to exchange application
layer data. (See flow chart below.) If a Session ID match is not layer data. (See flow chart below.) If a session ID match is not
found, the server generates a new session ID and the SSL client and found, the server generates a new session ID and the SSL client and
server perform a full handshake. server perform a full handshake.
Client Server Client Server
ClientHello --------> ClientHello -------->
ServerHello ServerHello
[change cipher spec] [change cipher spec]
<-------- Finished <-------- Finished
change cipher spec change cipher spec
Finished --------> Finished -------->
Application Data <-------> Application Data Application Data <-------> Application Data
The contents and significance of each message will be presented in The contents and significance of each message will be presented in
detail in the following sections. detail in the following sections.
5.6. Handshake protocol 5.6. Handshake Protocol
The SSL Handshake Protocol is one of the defined higher level clients The SSL handshake protocol is one of the defined higher level clients
of the SSL Record Protocol. This protocol is used to negotiate the of the SSL record protocol. This protocol is used to negotiate the
secure attributes of a session. Handshake messages are supplied to secure attributes of a session. Handshake messages are supplied to
the SSL Record Layer, where they are encapsulated within one or more the SSL record layer, where they are encapsulated within one or more
SSLPlaintext structures, which are processed and transmitted as SSLPlaintext structures, which are processed and transmitted as
specified by the current active session state. specified by the current active session state.
enum { enum {
hello_request(0), client_hello(1), server_hello(2), hello_request(0), client_hello(1), server_hello(2),
certificate(11), server_key_exchange (12), certificate(11), server_key_exchange (12),
certificate_request(13), server_hello_done(14), certificate_request(13), server_hello_done(14),
certificate_verify(15), client_key_exchange(16), certificate_verify(15), client_key_exchange(16),
finished(20), (255) finished(20), (255)
} HandshakeType; } HandshakeType;
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a fatal error. a fatal error.
5.6.1. Hello messages 5.6.1. Hello messages
The hello phase messages are used to exchange security enhancement The hello phase messages are used to exchange security enhancement
capabilities between the client and server. When a new session capabilities between the client and server. When a new session
begins, the CipherSpec encryption, hash, and compression algorithms begins, the CipherSpec encryption, hash, and compression algorithms
are initialized to null. The current CipherSpec is used for are initialized to null. The current CipherSpec is used for
renegotiation messages. renegotiation messages.
5.6.1.1. Hello request 5.6.1.1. Hello Request
The hello request message may be sent by the server at any time, but The hello request message may be sent by the server at any time, but
will be ignored by the client if the handshake protocol is already will be ignored by the client if the handshake protocol is already
underway. It is a simple notification that the client should begin underway. It is a simple notification that the client should begin
the negotiation process anew by sending a client hello message when the negotiation process anew by sending a client hello message when
convenient. convenient.
Note: Since handshake messages are intended to have transmission Note: Since handshake messages are intended to have transmission
precedence over application data, it is expected that the negotiation precedence over application data, it is expected that the negotiation
begin in no more than one or two times the transmission time of a begin in no more than one or two times the transmission time of a
maximum length application data message. maximum-length application data message.
After sending a hello request, servers should not repeat the request After sending a hello request, servers should not repeat the request
until the subsequent handshake negotiation is complete. A client until the subsequent handshake negotiation is complete. A client
that receives a hello request while in a handshake negotiation state that receives a hello request while in a handshake negotiation state
should simply ignore the message. should simply ignore the message.
The structure of a hello request message is as follows: The structure of a hello request message is as follows:
struct { } HelloRequest; struct { } HelloRequest;
5.6.1.2. Client hello 5.6.1.2. Client Hello
When a client first connects to a server it is required to send the When a client first connects to a server it is required to send the
client hello as its first message. The client can also send a client client hello as its first message. The client can also send a client
hello in response to a hello request or on its own initiative in hello in response to a hello request or on its own initiative in
order to renegotiate the security parameters in an existing order to renegotiate the security parameters in an existing
connection. The client hello message includes a random structure, connection. The client hello message includes a random structure,
which is used later in the protocol. which is used later in the protocol.
struct { struct {
uint32 gmt_unix_time; uint32 gmt_unix_time;
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When a client first connects to a server it is required to send the When a client first connects to a server it is required to send the
client hello as its first message. The client can also send a client client hello as its first message. The client can also send a client
hello in response to a hello request or on its own initiative in hello in response to a hello request or on its own initiative in
order to renegotiate the security parameters in an existing order to renegotiate the security parameters in an existing
connection. The client hello message includes a random structure, connection. The client hello message includes a random structure,
which is used later in the protocol. which is used later in the protocol.
struct { struct {
uint32 gmt_unix_time; uint32 gmt_unix_time;
opaque random_bytes[28]; opaque random_bytes[28];
} Random; } Random;
gmt_unix_time The current time and date in standard UNIX 32-bit gmt_unix_time: The current time and date in standard UNIX 32-bit
format according to the sender's internal clock. Clocks are not format according to the sender's internal clock. Clocks are not
required to be set correctly by the basic SSL Protocol; higher required to be set correctly by the basic SSL protocol; higher
level or application protocols may define additional requirements. level or application protocols may define additional requirements.
random_bytes 28 bytes generated by a secure random number generator. random_bytes: 28 bytes generated by a secure random number
generator.
The client hello message includes a variable length session The client hello message includes a variable-length session
identifier. If not empty, the value identifies a session between the identifier. If not empty, the value identifies a session between the
same client and server whose security parameters the client wishes to same client and server whose security parameters the client wishes to
reuse. The session identifier may be from an earlier connection, reuse. The session identifier may be from an earlier connection,
this connection, or another currently active connection. The second this connection, or another currently active connection. The second
option is useful if the client only wishes to update the random option is useful if the client only wishes to update the random
structures and derived values of a connection, while the third option structures and derived values of a connection, while the third option
makes it possible to establish several simultaneous independent makes it possible to establish several simultaneous independent
secure connections without repeating the full handshake protocol. secure connections without repeating the full handshake protocol.
The actual contents of the SessionID are defined by the server. The actual contents of the SessionID are defined by the server.
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The structure of the client hello is as follows. The structure of the client hello is as follows.
struct { struct {
ProtocolVersion client_version; ProtocolVersion client_version;
Random random; Random random;
SessionID session_id; SessionID session_id;
CipherSuite cipher_suites<2..2^16-1>; CipherSuite cipher_suites<2..2^16-1>;
CompressionMethod compression_methods<1..2^8-1>; CompressionMethod compression_methods<1..2^8-1>;
} ClientHello; } ClientHello;
client_version The version of the SSL protocol by which the client client_version: The version of the SSL protocol by which the client
wishes to communicate during this session. This should be the wishes to communicate during this session. This should be the
most recent (highest valued) version supported by the client. For most recent (highest valued) version supported by the client. For
this version of the specification, the version will be 3.0 (See this version of the specification, the version will be 3.0 (see
Appendix E for details about backward compatibility). Appendix E for details about backward compatibility).
random A client-generated random structure. random: A client-generated random structure.
session_id The ID of a session the client wishes to use for this session_id: The ID of a session the client wishes to use for this
connection. This field should be empty if no session_id is connection. This field should be empty if no session_id is
available or the client wishes to generate new security available or the client wishes to generate new security
parameters. parameters.
cipher_suites This is a list of the cryptographic options supported cipher_suites: This is a list of the cryptographic options supported
by the client, sorted with the client's first preference first. by the client, sorted with the client's first preference first.
If the session_id field is not empty (implying a session If the session_id field is not empty (implying a session
resumption request) this vector must include at least the resumption request), this vector must include at least the
cipher_suite from that session. Values are defined in cipher_suite from that session. Values are defined in
Appendix A.6. Appendix A.6.
compression_methods This is a list of the compression methods compression_methods: This is a list of the compression methods
supported by the client, sorted by client preference. If the supported by the client, sorted by client preference. If the
session_id field is not empty (implying a session resumption session_id field is not empty (implying a session resumption
request) this vector must include at least the compression_method request), this vector must include at least the compression_method
from that session. All implementations must support from that session. All implementations must support
CompressionMethod.null. CompressionMethod.null.
After sending the client hello message, the client waits for a server After sending the client hello message, the client waits for a server
hello message. Any other handshake message returned by the server hello message. Any other handshake message returned by the server
except for a hello request is treated as a fatal error. except for a hello request is treated as a fatal error.
Implementation note: Application data may not be sent before a Implementation note: Application data may not be sent before a
finished message has been sent. Transmitted application data is finished message has been sent. Transmitted application data is
known to be insecure until a valid finished message has been known to be insecure until a valid finished message has been
received. This absolute restriction is relaxed if there is a received. This absolute restriction is relaxed if there is a
current, non-null encryption on this connection. current, non-null encryption on this connection.
Forward compatibility note: In the interests of forward Forward compatibility note: In the interests of forward
compatibility, it is permitted for a client hello message to include compatibility, it is permitted for a client hello message to include
extra data after the compression methods. This data must be included extra data after the compression methods. This data must be included
in the handshake hashes, but must otherwise be ignored. in the handshake hashes, but must otherwise be ignored.
5.6.1.3. Server hello 5.6.1.3. Server Hello
The server processes the client hello message and responds with The server processes the client hello message and responds with
either a handshake_failure alert or server hello message. either a handshake_failure alert or server hello message.
struct { struct {
ProtocolVersion server_version; ProtocolVersion server_version;
Random random; Random random;
SessionID session_id; SessionID session_id;
CipherSuite cipher_suite; CipherSuite cipher_suite;
CompressionMethod compression_method; CompressionMethod compression_method;
} ServerHello; } ServerHello;
server_version This field will contain the lower of that suggested server_version: This field will contain the lower of that suggested
by the client in the client hello and the highest supported by the by the client in the client hello and the highest supported by the
server. For this version of the specification, the version will server. For this version of the specification, the version will
be 3.0 (See Appendix E for details about backward compatibility). be 3.0 (see Appendix E for details about backward compatibility).
random This structure is generated by the server and must be random: This structure is generated by the server and must be
different from (and independent of) ClientHello.random. different from (and independent of) ClientHello.random.
session_id This is the identity of the session corresponding to this session_id: This is the identity of the session corresponding to
connection. If the ClientHello.session_id was non-empty, the this connection. If the ClientHello.session_id was non-empty, the
server will look in its session cache for a match. If a match is server will look in its session cache for a match. If a match is
found and the server is willing to establish the new connection found and the server is willing to establish the new connection
using the specified session state, the server will respond with using the specified session state, the server will respond with
the same value as was supplied by the client. This indicates a the same value as was supplied by the client. This indicates a
resumed session and dictates that the parties must proceed resumed session and dictates that the parties must proceed
directly to the finished messages. Otherwise this field will directly to the finished messages. Otherwise, this field will
contain a different value identifying the new session. The server contain a different value identifying the new session. The server
may return an empty session_id to indicate that the session will may return an empty session_id to indicate that the session will
not be cached and therefore cannot be resumed. not be cached and therefore cannot be resumed.
cipher_suite The single cipher suite selected by the server from the cipher_suite: The single cipher suite selected by the server from
list in ClientHello.cipher_suites. For resumed sessions this the list in ClientHello.cipher_suites. For resumed sessions, this
field is the value from the state of the session being resumed. field is the value from the state of the session being resumed.
compression_method The single compression algorithm selected by the compression_method: The single compression algorithm selected by the
server from the list in ClientHello.compression_methods. For server from the list in ClientHello.compression_methods. For
resumed sessions this field is the value from the resumed session resumed sessions, this field is the value from the resumed session
state. state.
5.6.2. Server certificate 5.6.2. Server Certificate
If the server is to be authenticated (which is generally the case), If the server is to be authenticated (which is generally the case),
the server sends its certificate immediately following the server the server sends its certificate immediately following the server
hello message. The certificate type must be appropriate for the hello message. The certificate type must be appropriate for the
selected cipher suite's key exchange algorithm, and is generally an selected cipher suite's key exchange algorithm, and is generally an
X.509.v3 certificate (or a modified X.509 certificate in the case of X.509.v3 certificate (or a modified X.509 certificate in the case of
FORTEZZA(tm) [FOR]). The same message type will be used for the FORTEZZA(tm) [FOR]). The same message type will be used for the
client's response to a certificate request message. client's response to a certificate request message.
opaque ASN.1Cert<1..2^24-1>; opaque ASN.1Cert<1..2^24-1>;
struct { struct {
ASN.1Cert certificate_list<1..2^24-1>; ASN.1Cert certificate_list<1..2^24-1>;
} Certificate; } Certificate;
certificate_list This is a sequence (chain) of X.509.v3 certificate_list: This is a sequence (chain) of X.509.v3
certificates, ordered with the sender's certificate first followed certificates, ordered with the sender's certificate first followed
by any certificate authority certificates proceeding sequentially by any certificate authority certificates proceeding sequentially
upward. upward.
Note: PKCS #7 [PKCS7] is not used as the format for the certificate Note: PKCS #7 [PKCS7] is not used as the format for the certificate
vector because PKCS #6 [PKCS6] extended certificates are not used. vector because PKCS #6 [PKCS6] extended certificates are not used.
Also PKCS #7 defines a SET rather than a SEQUENCE, making the task of Also, PKCS #7 defines a Set rather than a Sequence, making the task
parsing the list more difficult. of parsing the list more difficult.
5.6.3. Server key exchange message 5.6.3. Server Key Exchange Message
The server key exchange message is sent by the server if it has no The server key exchange message is sent by the server if it has no
certificate, has a certificate only used for signing (e.g., DSS [DSS] certificate, has a certificate only used for signing (e.g., DSS [DSS]
certificates, signing-only RSA [RSA] certificates), or FORTEZZA KEA certificates, signing-only RSA [RSA] certificates), or FORTEZZA KEA
key exchange is used. This message is not used if the server key exchange is used. This message is not used if the server
certificate contains Diffie-Hellman [DH1] parameters. certificate contains Diffie-Hellman [DH1] parameters.
Note: According to current US export law, RSA moduli larger than 512 Note: According to current US export law, RSA moduli larger than 512
bits may not be used for key exchange in software exported from the bits may not be used for key exchange in software exported from the
US. With this message, larger RSA keys may be used as signature-only US. With this message, larger RSA keys may be used as signature-only
certificates to sign temporary shorter RSA keys for key exchange. certificates to sign temporary shorter RSA keys for key exchange.
enum { rsa, diffie_hellman, fortezza_kea } enum { rsa, diffie_hellman, fortezza_kea }
KeyExchangeAlgorithm; KeyExchangeAlgorithm;
struct { struct {
opaque rsa_modulus<1..2^16-1>; opaque rsa_modulus<1..2^16-1>;
opaque rsa_exponent<1..2^16-1>; opaque rsa_exponent<1..2^16-1>;
} ServerRSAParams; } ServerRSAParams;
rsa_modulus The modulus of the server's temporary RSA key. rsa_modulus: The modulus of the server's temporary RSA key.
rsa_exponent The public exponent of the server's temporary RSA key. rsa_exponent: The public exponent of the server's temporary RSA key.
struct { struct {
opaque dh_p<1..2^16-1>; opaque dh_p<1..2^16-1>;
opaque dh_g<1..2^16-1>; opaque dh_g<1..2^16-1>;
opaque dh_Ys<1..2^16-1>; opaque dh_Ys<1..2^16-1>;
} ServerDHParams; /* Ephemeral DH parameters */ } ServerDHParams; /* Ephemeral DH parameters */
dh_p The prime modulus used for the Diffie-Hellman operation. dh_p: The prime modulus used for the Diffie-Hellman operation.
dh_g The generator used for the Diffie-Hellman operation. dh_g: The generator used for the Diffie-Hellman operation.
dh_Ys The server's Diffie-Hellman public value (gX mod p). dh_Ys: The server's Diffie-Hellman public value (gX mod p).
struct { struct {
opaque r_s [128]; opaque r_s [128];
} ServerFortezzaParams; } ServerFortezzaParams;
r_s Server random number for FORTEZZA KEA (Key Exchange Algorithm). r_s: Server random number for FORTEZZA KEA (Key Exchange Algorithm).
struct { struct {
select (KeyExchangeAlgorithm) { select (KeyExchangeAlgorithm) {
case diffie_hellman: case diffie_hellman:
ServerDHParams params; ServerDHParams params;
Signature signed_params; Signature signed_params;
case rsa: case rsa:
ServerRSAParams params; ServerRSAParams params;
Signature signed_params; Signature signed_params;
case fortezza_kea: case fortezza_kea:
ServerFortezzaParams params; ServerFortezzaParams params;
}; };
} ServerKeyExchange; } ServerKeyExchange;
params The server's key exchange parameters. params: The server's key exchange parameters.
signed_params A hash of the corresponding params value, with the signed_params: A hash of the corresponding params value, with the
signature appropriate to that hash applied. signature appropriate to that hash applied.
md5_hash MD5(ClientHello.random + ServerHello.random + md5_hash: MD5(ClientHello.random + ServerHello.random +
ServerParams); ServerParams);
sha_hash SHA(ClientHello.random + ServerHello.random + sha_hash: SHA(ClientHello.random + ServerHello.random +
ServerParams); ServerParams);
enum { anonymous, rsa, dsa } SignatureAlgorithm; enum { anonymous, rsa, dsa } SignatureAlgorithm;
digitally-signed struct { digitally-signed struct {
select(SignatureAlgorithm) { select(SignatureAlgorithm) {
case anonymous: struct { }; case anonymous: struct { };
case rsa: case rsa:
opaque md5_hash[16]; opaque md5_hash[16];
opaque sha_hash[20]; opaque sha_hash[20];
case dsa: case dsa:
opaque sha_hash[20]; opaque sha_hash[20];
}; };
} Signature; } Signature;
5.6.4. Certificate request 5.6.4. Certificate Request
A non-anonymous server can optionally request a certificate from the A non-anonymous server can optionally request a certificate from the
client, if appropriate for the selected cipher suite. client, if appropriate for the selected cipher suite.
enum { enum {
rsa_sign(1), dss_sign(2), rsa_fixed_dh(3), dss_fixed_dh(4), rsa_sign(1), dss_sign(2), rsa_fixed_dh(3), dss_fixed_dh(4),
rsa_ephemeral_dh(5), dss_ephemeral_dh(6), fortezza_kea(20), rsa_ephemeral_dh(5), dss_ephemeral_dh(6), fortezza_kea(20),
(255) (255)
} ClientCertificateType; } ClientCertificateType;
opaque DistinguishedName<1..2^16-1>; opaque DistinguishedName<1..2^16-1>;
struct { struct {
ClientCertificateType certificate_types<1..2^8-1>; ClientCertificateType certificate_types<1..2^8-1>;
DistinguishedName certificate_authorities<3..2^16-1>; DistinguishedName certificate_authorities<3..2^16-1>;
} CertificateRequest; } CertificateRequest;
certificate_types This field is a list of the types of certificates certificate_types: This field is a list of the types of certificates
requested, sorted in order of the server's preference. requested, sorted in order of the server's preference.
certificate_authorities A list of the distinguished names of certificate_authorities: A list of the distinguished names of
acceptable certificate authorities. acceptable certificate authorities.
Note: DistinguishedName is derived from [X509]. Note: DistinguishedName is derived from [X509].
Note: It is a fatal handshake_failure alert for an anonymous server Note: It is a fatal handshake_failure alert for an anonymous server
to request client identification. to request client identification.
5.6.5. Server hello done 5.6.5. Server Hello Done
The server hello done message is sent by the server to indicate the The server hello done message is sent by the server to indicate the
end of the server hello and associated messages. After sending this end of the server hello and associated messages. After sending this
message the server will wait for a client response. message, the server will wait for a client response.
struct { } ServerHelloDone; struct { } ServerHelloDone;
Upon receipt of the server hello done message the client should Upon receipt of the server hello done message the client should
verify that the server provided a valid certificate if required and verify that the server provided a valid certificate if required and
check that the server hello parameters are acceptable. check that the server hello parameters are acceptable.
5.6.6. Client certificate 5.6.6. Client Certificate
This is the first message the client can send after receiving a This is the first message the client can send after receiving a
server hello done message. This message is only sent if the server server hello done message. This message is only sent if the server
requests a certificate. If no suitable certificate is available, the requests a certificate. If no suitable certificate is available, the
client should send a no_certificate alert instead. This alert is client should send a no_certificate alert instead. This alert is
only a warning, however the server may respond with a fatal handshake only a warning; however, the server may respond with a fatal
failure alert if client authentication is required. Client handshake failure alert if client authentication is required. Client
certificates are sent using the Certificate defined in Section 5.6.2. certificates are sent using the certificate defined in Section 5.6.2.
Note: Client Diffie-Hellman certificates must match the server Note: Client Diffie-Hellman certificates must match the server
specified Diffie-Hellman parameters. specified Diffie-Hellman parameters.
5.6.7. Client key exchange message 5.6.7. Client Key Exchange Message
The choice of messages depends on which public key algorithm(s) has The choice of messages depends on which public key algorithm(s) has
(have) been selected. See Section 5.6.3 for the KeyExchangeAlgorithm (have) been selected. See Section 5.6.3 for the KeyExchangeAlgorithm
definition. definition.
struct { struct {
select (KeyExchangeAlgorithm) { select (KeyExchangeAlgorithm) {
case rsa: EncryptedPreMasterSecret; case rsa: EncryptedPreMasterSecret;
case diffie_hellman: ClientDiffieHellmanPublic; case diffie_hellman: ClientDiffieHellmanPublic;
case fortezza_kea: FortezzaKeys; case fortezza_kea: FortezzaKeys;
} exchange_keys; } exchange_keys;
} ClientKeyExchange; } ClientKeyExchange;
The information to select the appropriate record structure is in the The information to select the appropriate record structure is in the
pending session state (see Section 5.1). pending session state (see Section 5.1).
5.6.7.1. RSA encrypted premaster secret message 5.6.7.1. RSA Encrypted Premaster Secret Message
If RSA is being used for key agreement and authentication, the client If RSA is being used for key agreement and authentication, the client
generates a 48-byte pre-master secret, encrypts it under the public generates a 48-byte premaster secret, encrypts it under the public
key from the server's certificate or temporary RSA key from a server key from the server's certificate or temporary RSA key from a server
key exchange message, and sends the result in an encrypted premaster key exchange message, and sends the result in an encrypted premaster
secret message. secret message.
struct { struct {
ProtocolVersion client_version; ProtocolVersion client_version;
opaque random[46]; opaque random[46];
} PreMasterSecret; } PreMasterSecret;
client_version The latest (newest) version supported by the client. client_version: The latest (newest) version supported by the client.
This is used to detect version roll-back attacks. This is used to detect version roll-back attacks.
random 46 securely-generated random bytes. random: 46 securely-generated random bytes.
struct { struct {
public-key-encrypted PreMasterSecret pre_master_secret; public-key-encrypted PreMasterSecret pre_master_secret;
} EncryptedPreMasterSecret; } EncryptedPreMasterSecret;
pre_master_secret This random value is generated by the client and pre_master_secret: This random value is generated by the client and
is used to generate the master secret, as specified in is used to generate the master secret, as specified in
Section 6.1. Section 6.1.
5.6.7.2. FORTEZZA key exchange message 5.6.7.2. FORTEZZA Key Exchange Message
Under FORTEZZA, the client derives a Token Encryption Key (TEK) using Under FORTEZZA, the client derives a token encryption key (TEK) using
the FORTEZZA Key Exchange Algorithm (KEA). The client's KEA the FORTEZZA Key Exchange Algorithm (KEA). The client's KEA
calculation uses the public key in the server's certificate along calculation uses the public key in the server's certificate along
with private parameters in the client's token. The client sends with private parameters in the client's token. The client sends
public parameters needed for the server to generate the TEK, using public parameters needed for the server to generate the TEK, using
its own private parameters. The client generates session keys, wraps its own private parameters. The client generates session keys, wraps
them using the TEK, and sends the results to the server. The client them using the TEK, and sends the results to the server. The client
generates IV's for the session keys and TEK and sends them also. The generates IVs for the session keys and TEK and sends them also. The
client generates a random 48-byte premaster secret, encrypts it using client generates a random 48-byte premaster secret, encrypts it using
the TEK, and sends the result: the TEK, and sends the result:
struct { struct {
opaque y_c<0..128>; opaque y_c<0..128>;
opaque r_c[128]; opaque r_c[128];
opaque y_signature[40]; opaque y_signature[40];
opaque wrapped_client_write_key[12]; opaque wrapped_client_write_key[12];
opaque wrapped_server_write_key[12]; opaque wrapped_server_write_key[12];
opaque client_write_iv[24]; opaque client_write_iv[24];
opaque server_write_iv[24]; opaque server_write_iv[24];
opaque master_secret_iv[24]; opaque master_secret_iv[24];
block-ciphered opaque encrypted_pre_master_secret[48]; block-ciphered opaque encrypted_pre_master_secret[48];
} FortezzaKeys; } FortezzaKeys;
y_signature y_signature is the signature of the KEA public key, y_signature: y_signature is the signature of the KEA public key,
signed with the client's DSS private key. signed with the client's DSS private key.
y_c The client's Yc value (public key) for the KEA calculation. If y_c: The client's Yc value (public key) for the KEA calculation. If
the client has sent a certificate, and its KEA public key is the client has sent a certificate, and its KEA public key is
suitable, this value must be empty since the certificate already suitable, this value must be empty since the certificate already
contains this value. If the client sent a certificate without a contains this value. If the client sent a certificate without a
suitable public key, y_c is used and y_signature is the KEA public suitable public key, y_c is used and y_signature is the KEA public
key signed with the client's DSS private key. For this value to key signed with the client's DSS private key. For this value to
be used, it must be between 64 and 128 bytes. be used, it must be between 64 and 128 bytes.
r_c The client's Rc value for the KEA calculation. r_c: The client's Rc value for the KEA calculation.
wrapped_client_write_key This is the client's write key, wrapped by wrapped_client_write_key: This is the client's write key, wrapped by
the TEK. the TEK.
wrapped_server_write_key This is the server's write key, wrapped by wrapped_server_write_key: This is the server's write key, wrapped by
the TEK. the TEK.
client_write_iv The IV for the client write key. client_write_iv: The IV for the client write key.
server_write_iv The IV for the server write key. server_write_iv: The IV for the server write key.
master_secret_iv This is the IV for the TEK used to encrypt the pre- master_secret_iv: This is the IV for the TEK used to encrypt the
master secret. premaster secret.
pre_master_secret A random value, generated by the client and used pre_master_secret: A random value, generated by the client and used
to generate the master secret, as specified in Section 6.1. In to generate the master secret, as specified in Section 6.1. In
the the above structure, it is encrypted using the TEK. the above structure, it is encrypted using the TEK.
5.6.7.3. Client Diffie-Hellman public value 5.6.7.3. Client Diffie-Hellman Public Value
This structure conveys the client's Diffie-Hellman public value (Yc) This structure conveys the client's Diffie-Hellman public value (Yc)
if it was not already included in the client's certificate. The if it was not already included in the client's certificate. The
encoding used for Yc is determined by the enumerated encoding used for Yc is determined by the enumerated
PublicValueEncoding. PublicValueEncoding.
enum { implicit, explicit } PublicValueEncoding; enum { implicit, explicit } PublicValueEncoding;
implicit If the client certificate already contains the public implicit: If the client certificate already contains the public
value, then it is implicit and Yc does not need to be sent again. value, then it is implicit and Yc does not need to be sent again.
explicit Yc needs to be sent. explicit: Yc needs to be sent.
struct { struct {
select (PublicValueEncoding) { select (PublicValueEncoding) {
case implicit: struct { }; case implicit: struct { };
case explicit: opaque dh_Yc<1..2^16-1>; case explicit: opaque dh_Yc<1..2^16-1>;
} dh_public; } dh_public;
} ClientDiffieHellmanPublic; } ClientDiffieHellmanPublic;
dh_Yc The client's Diffie-Hellman public value (Yc). dh_Yc: The client's Diffie-Hellman public value (Yc).
5.6.8. Certificate verify 5.6.8. Certificate Verify
This message is used to provide explicit verification of a client This message is used to provide explicit verification of a client
certificate. This message is only sent following any client certificate. This message is only sent following any client
certificate that has signing capability (i.e. all certificates except certificate that has signing capability (i.e., all certificates
those containing fixed Diffie-Hellman parameters). except those containing fixed Diffie-Hellman parameters).
struct { struct {
Signature signature; Signature signature;
} CertificateVerify; } CertificateVerify;
CertificateVerify.signature.md5_hash CertificateVerify.signature.md5_hash
MD5(master_secret + pad_2 + MD5(master_secret + pad_2 +
MD5(handshake_messages + master_secret + pad_1)); MD5(handshake_messages + master_secret + pad_1));
Certificate.signature.sha_hash Certificate.signature.sha_hash
SHA(master_secret + pad_2 + SHA(master_secret + pad_2 +
SHA(handshake_messages + master_secret + pad_1)); SHA(handshake_messages + master_secret + pad_1));
pad_1 This is identical to the pad_1 defined in section 5.2.3.1. pad_1: This is identical to the pad_1 defined in Section 5.2.3.1.
pad_2 This is identical to the pad_2 defined in section 5.2.3.1. pad_2: This is identical to the pad_2 defined in Section 5.2.3.1.
Here handshake_messages refers to all handshake messages starting at Here, handshake_messages refers to all handshake messages starting at
client hello up to but not including this message. client hello up to but not including this message.
5.6.9. Finished 5.6.9. Finished
A finished message is always sent immediately after a change cipher A finished message is always sent immediately after a change cipher
specs message to verify that the key exchange and authentication spec message to verify that the key exchange and authentication
processes were successful. The finished message is the first processes were successful. The finished message is the first
protected with the just-negotiated algorithms, keys, and secrets. No protected with the just-negotiated algorithms, keys, and secrets. No
acknowledgment of the finished message is required; parties may begin acknowledgment of the finished message is required; parties may begin
sending encrypted data immediately after sending the finished sending encrypted data immediately after sending the finished
message. Recipients of finished messages must verify that the message. Recipients of finished messages must verify that the
contents are correct. contents are correct.
enum { client(0x434C4E54), server(0x53525652) } Sender; enum { client(0x434C4E54), server(0x53525652) } Sender;
struct { struct {
opaque md5_hash[16]; opaque md5_hash[16];
opaque sha_hash[20]; opaque sha_hash[20];
} Finished; } Finished;
md5_hash MD5(master_secret + pad2 + MD5(handshake_messages + Sender md5_hash: MD5(master_secret + pad2 + MD5(handshake_messages + Sender
+ master_secret + pad1)); + master_secret + pad1));
sha_hash SHA(master_secret + pad2 + SHA(handshake_messages + Sender sha_hash: SHA(master_secret + pad2 + SHA(handshake_messages + Sender
+ master_secret + pad1)); + master_secret + pad1));
handshake_messages All of the data from all handshake messages up to handshake_messages: All of the data from all handshake messages up
but not including this message. This is only data visible at the to but not including this message. This is only data visible at
handshake layer and does not include record layer headers. the handshake layer and does not include record layer headers.
It is a fatal error if a finished message is not preceeded by a It is a fatal error if a finished message is not preceeded by a
change cipher spec message at the appropriate point in the handshake. change cipher spec message at the appropriate point in the handshake.
The hash contained in finished messages sent by the server The hash contained in finished messages sent by the server
incorporate Sender.server; those sent by the client incorporate incorporate Sender.server; those sent by the client incorporate
Sender.client. The value handshake_messages includes all handshake Sender.client. The value handshake_messages includes all handshake
messages starting at client hello up to, but not including, this messages starting at client hello up to but not including this
finished message. This may be different from handshake_messages in finished message. This may be different from handshake_messages in
Section 5.6.8 because it would include the certificate verify message Section 5.6.8 because it would include the certificate verify message
(if sent). (if sent).
Note: Change cipher spec messages are not handshake messages and are Note: Change cipher spec messages are not handshake messages and are
not included in the hash computations. not included in the hash computations.
5.7. Application data protocol 5.7. Application Data Protocol
Application data messages are carried by the Record Layer and are Application data messages are carried by the record layer and are
fragmented, compressed and encrypted based on the current connection fragmented, compressed, and encrypted based on the current connection
state. The messages are treated as transparent data to the record state. The messages are treated as transparent data to the record
layer. layer.
6. Cryptographic computations 6. Cryptographic Computations
The key exchange, authentication, encryption, and MAC algorithms are The key exchange, authentication, encryption, and MAC algorithms are
determined by the cipher_suite selected by the server and revealed in determined by the cipher_suite selected by the server and revealed in
the server hello message. the server hello message.
6.1. Asymmetric cryptographic computations 6.1. Asymmetric Cryptographic Computations
The asymmetric algorithms are used in the handshake protocol to The asymmetric algorithms are used in the handshake protocol to
authenticate parties and to generate shared keys and secrets. authenticate parties and to generate shared keys and secrets.
For Diffie-Hellman, RSA, and FORTEZZA, the same algorithm is used to For Diffie-Hellman, RSA, and FORTEZZA, the same algorithm is used to
convert the pre_master_secret into the master_secret. The convert the pre_master_secret into the master_secret. The
pre_master_secret should be deleted from memory once the pre_master_secret should be deleted from memory once the
master_secret has been computed. master_secret has been computed.
master_secret = master_secret =
skipping to change at page 36, line 40 skipping to change at page 36, line 45
6.1.1. RSA 6.1.1. RSA
When RSA is used for server authentication and key exchange, a 48- When RSA is used for server authentication and key exchange, a 48-
byte pre_master_secret is generated by the client, encrypted under byte pre_master_secret is generated by the client, encrypted under
the server's public key, and sent to the server. The server uses its the server's public key, and sent to the server. The server uses its
private key to decrypt the pre_master_secret. Both parties then private key to decrypt the pre_master_secret. Both parties then
convert the pre_master_secret into the master_secret, as specified convert the pre_master_secret into the master_secret, as specified
above. above.
RSA digital signatures are performed using PKCS #1 [PKCS1] block type RSA digital signatures are performed using PKCS #1 [PKCS1] block
1. RSA public key encryption is performed using PKCS #1 block type type 1. RSA public key encryption is performed using PKCS #1 block
2. type 2.
6.1.2. Diffie-Hellman 6.1.2. Diffie-Hellman
A conventional Diffie-Hellman computation is performed. The A conventional Diffie-Hellman computation is performed. The
negotiated key (Z) is used as the pre_master_secret, and is converted negotiated key (Z) is used as the pre_master_secret, and is converted
into the master_secret, as specified above. into the master_secret, as specified above.
Note: Diffie-Hellman parameters are specified by the server, and may Note: Diffie-Hellman parameters are specified by the server, and may
be either ephemeral or contained within the server's certificate. be either ephemeral or contained within the server's certificate.
6.1.3. FORTEZZA 6.1.3. FORTEZZA
A random 48-byte pre_master_secret is sent encrypted under the TEK A random 48-byte pre_master_secret is sent encrypted under the TEK
and its IV. The server decrypts the pre_master_secret and converts and its IV. The server decrypts the pre_master_secret and converts
it into a master_secret, as specified above. Bulk cipher keys and it into a master_secret, as specified above. Bulk cipher keys and
IVs for encryption are generated by the client's token and exchanged IVs for encryption are generated by the client's token and exchanged
in the key exchange message; the master_secret is only used for MAC in the key exchange message; the master_secret is only used for MAC
computations. computations.
6.2. Symmetric cryptographic calculations and the CipherSpec 6.2. Symmetric Cryptographic Calculations and the CipherSpec
The technique used to encrypt and verify the integrity of SSL records The technique used to encrypt and verify the integrity of SSL records
is specified by the currently active CipherSpec. A typical example is specified by the currently active CipherSpec. A typical example
would be to encrypt data using DES and generate authentication codes would be to encrypt data using DES and generate authentication codes
using MD5. The encryption and MAC algorithms are set to using MD5. The encryption and MAC algorithms are set to
SSL_NULL_WITH_NULL_NULL at the beginning of the SSL Handshake SSL_NULL_WITH_NULL_NULL at the beginning of the SSL handshake
Protocol, indicating that no message authentication or encryption is protocol, indicating that no message authentication or encryption is
performed. The handshake protocol is used to negotiate a more secure performed. The handshake protocol is used to negotiate a more secure
CipherSpec and to generate cryptographic keys. CipherSpec and to generate cryptographic keys.
6.2.1. The master secret 6.2.1. The Master Secret
Before secure encryption or integrity verification can be performed Before secure encryption or integrity verification can be performed
on records, the client and server need to generate shared secret on records, the client and server need to generate shared secret
information known only to themselves. This value is a 48-byte information known only to themselves. This value is a 48-byte
quantity called the master secret. The master secret is used to quantity called the master secret. The master secret is used to
generate keys and secrets for encryption and MAC computations. Some generate keys and secrets for encryption and MAC computations. Some
algorithms, such as FORTEZZA, may have their own procedure for algorithms, such as FORTEZZA, may have their own procedure for
generating encryption keys (the master secret is used only for MAC generating encryption keys (the master secret is used only for MAC
computations in FORTEZZA). computations in FORTEZZA).
6.2.2. Converting the master secret into keys and MAC secrets 6.2.2. Converting the Master Secret into Keys and MAC Secrets
The master secret is hashed into a sequence of secure bytes, which The master secret is hashed into a sequence of secure bytes, which
are assigned to the MAC secrets, keys, and non-export IVs required by are assigned to the MAC secrets, keys, and non-export IVs required by
the current CipherSpec (see Appendix A.7). CipherSpecs require a the current CipherSpec (see Appendix A.7). CipherSpecs require a
client write MAC secret, a server write MAC secret, a client write client write MAC secret, a server write MAC secret, a client write
key, a server write key, a client write IV, and a server write IV, key, a server write key, a client write IV, and a server write IV,
which are generated from the master secret in that order. Unused which are generated from the master secret in that order. Unused
values, such as FORTEZZA keys communicated in the KeyExchange values, such as FORTEZZA keys communicated in the KeyExchange
message, are empty. The following inputs are available to the key message, are empty. The following inputs are available to the key
definition process: definition process:
skipping to change at page 38, line 26 skipping to change at page 38, line 29
MD5(master_secret + SHA(`A' + master_secret + MD5(master_secret + SHA(`A' + master_secret +
ServerHello.random + ServerHello.random +
ClientHello.random)) + ClientHello.random)) +
MD5(master_secret + SHA(`BB' + master_secret + MD5(master_secret + SHA(`BB' + master_secret +
ServerHello.random + ServerHello.random +
ClientHello.random)) + ClientHello.random)) +
MD5(master_secret + SHA(`CCC' + master_secret + MD5(master_secret + SHA(`CCC' + master_secret +
ServerHello.random + ServerHello.random +
ClientHello.random)) + [...]; ClientHello.random)) + [...];
until enough output has been generated. Then the key_block is until enough output has been generated. Then, the key_block is
partitioned as follows. partitioned as follows.
client_write_MAC_secret[CipherSpec.hash_size] client_write_MAC_secret[CipherSpec.hash_size]
server_write_MAC_secret[CipherSpec.hash_size] server_write_MAC_secret[CipherSpec.hash_size]
client_write_key[CipherSpec.key_material] client_write_key[CipherSpec.key_material]
server_write_key[CipherSpec.key_material] server_write_key[CipherSpec.key_material]
client_write_IV[CipherSpec.IV_size] /* non-export ciphers */ client_write_IV[CipherSpec.IV_size] /* non-export ciphers */
server_write_IV[CipherSpec.IV_size] /* non-export ciphers */ server_write_IV[CipherSpec.IV_size] /* non-export ciphers */
Any extra key_block material is discarded. Any extra key_block material is discarded.
skipping to change at page 39, line 14 skipping to change at page 39, line 14
Exportable encryption algorithms derive their IVs from the random Exportable encryption algorithms derive their IVs from the random
messages: messages:
client_write_IV = MD5(ClientHello.random + ServerHello.random); client_write_IV = MD5(ClientHello.random + ServerHello.random);
server_write_IV = MD5(ServerHello.random + ClientHello.random); server_write_IV = MD5(ServerHello.random + ClientHello.random);
MD5 outputs are trimmed to the appropriate size by discarding the MD5 outputs are trimmed to the appropriate size by discarding the
least-significant bytes. least-significant bytes.
6.2.2.1. Export key generation example 6.2.2.1. Export Key Generation Example
SSL_RSA_EXPORT_WITH_RC2_CBC_40_MD5 requires five random bytes for SSL_RSA_EXPORT_WITH_RC2_CBC_40_MD5 requires five random bytes for
each of the two encryption keys and 16 bytes for each of the MAC each of the two encryption keys and 16 bytes for each of the MAC
keys, for a total of 42 bytes of key material. MD5 produces 16 bytes keys, for a total of 42 bytes of key material. MD5 produces 16 bytes
of output per call, so three calls to MD5 are required. The MD5 of output per call, so three calls to MD5 are required. The MD5
outputs are concatenated into a 48-byte key_block with the first MD5 outputs are concatenated into a 48-byte key_block with the first MD5
call providing bytes zero through 15, the second providing bytes 16 call providing bytes zero through 15, the second providing bytes 16
through 31, etc. The key_block is partitioned, and the write keys through 31, etc. The key_block is partitioned, and the write keys
are salted because this is an exportable encryption algorithm. are salted because this is an exportable encryption algorithm.
skipping to change at page 39, line 40 skipping to change at page 39, line 40
ClientHello.random + ClientHello.random +
ServerHello.random)[0..15]; ServerHello.random)[0..15];
final_server_write_key = MD5(server_write_key + final_server_write_key = MD5(server_write_key +
ServerHello.random + ServerHello.random +
ClientHello.random)[0..15]; ClientHello.random)[0..15];
client_write_IV = MD5(ClientHello.random + client_write_IV = MD5(ClientHello.random +
ServerHello.random)[0..7]; ServerHello.random)[0..7];
server_write_IV = MD5(ServerHello.random + server_write_IV = MD5(ServerHello.random +
ClientHello.random)[0..7]; ClientHello.random)[0..7];
7. Security considerations 7. Security Considerations
See Appendix F. See Appendix F.
8. IANA considerations 8. Informative References
This document has no actions for IANA.
9. Informative References
[DH1] Diffie, W. and M. Hellman, "New Directions in [DH1] Diffie, W. and M. Hellman, "New Directions in
Cryptography", IEEE Transactions on Information Theory V. Cryptography", IEEE Transactions on Information Theory V.
IT-22, n. 6, pp. 74-84, June 1977. IT-22, n. 6, pp. 74-84, June 1977.
[SSL-2] Hickman, K., "The SSL Protocol", February 1995. [SSL-2] Hickman, K., "The SSL Protocol", February 1995.
[3DES] Tuchman, W., "Hellman Presents No Shortcut Solutions To [3DES] Tuchman, W., "Hellman Presents No Shortcut Solutions To
DES", IEEE Spectrum, v. 16, n. 7, pp40-41. , July 1979. DES", IEEE Spectrum, v. 16, n. 7, pp 40-41, July 1979.
[DES] ANSI X3.106, "American National Standard for Information [DES] ANSI X3.106, "American National Standard for Information
Systems-Data Link Encryption", American National Standards Systems-Data Link Encryption", American National
Institute , 1983. Standards Institute, 1983.
[DSS] NIST FIPS PUB 186, "Digital Signature Standard", National [DSS] NIST FIPS PUB 186, "Digital Signature Standard", National
Institute of Standards and Technology, U.S. Department of Institute of Standards and Technology U.S. Department of
Commerce , May 1994. Commerce, May 1994.
[FOR] NSA X22, "FORTEZZA: Application Implementers Guide", [FOR] NSA X22, "FORTEZZA: Application Implementers Guide",
Document # PD4002103-1.01 , April 1995. Document # PD4002103-1.01, April 1995.
[RFC0959] Postel, J. and J. Reynolds, "File Transfer Protocol", [RFC0959] Postel, J. and J. Reynolds, "File Transfer Protocol",
STD 9, RFC 959, October 1985. STD 9, RFC 959, October 1985.
[RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791, [RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791,
September 1981. September 1981.
[RFC1945] Berners-Lee, T., Fielding, R., and H. Nielsen, "Hypertext [RFC1945] Berners-Lee, T., Fielding, R., and H. Nielsen, "Hypertext
Transfer Protocol -- HTTP/1.0", RFC 1945, May 1996. Transfer Protocol -- HTTP/1.0", RFC 1945, May 1996.
[RFC1319] Kaliski, B., "The MD2 Message-Digest Algorithm", RFC 1319,
April 1992.
[RFC1321] Rivest, R., "The MD5 Message-Digest Algorithm", RFC 1321, [RFC1321] Rivest, R., "The MD5 Message-Digest Algorithm", RFC 1321,
April 1992. April 1992.
[RFC0793] Postel, J., "Transmission Control Protocol", STD 7, [RFC0793] Postel, J., "Transmission Control Protocol", STD 7,
RFC 793, September 1981. RFC 793, September 1981.
[RFC0854] Postel, J. and J. Reynolds, "Telnet Protocol [RFC0854] Postel, J. and J. Reynolds, "Telnet Protocol
Specification", STD 8, RFC 854, May 1983. Specification", STD 8, RFC 854, May 1983.
[RFC1832] Srinivasan, R., "XDR: External Data Representation [RFC1832] Srinivasan, R., "XDR: External Data Representation
Standard", RFC 1832, August 1995. Standard", RFC 1832, August 1995.
[RFC2104] Krawczyk, H., Bellare, M., and R. Canetti, "HMAC: Keyed- [RFC2104] Krawczyk, H., Bellare, M., and R. Canetti, "HMAC: Keyed-
Hashing for Message Authentication", RFC 2104, Hashing for Message Authentication", RFC 2104,
February 1997. February 1997.
[IDEA] Lai, X., "On the Design and Security of Block Ciphers", [IDEA] Lai, X., "On the Design and Security of Block Ciphers",
ETH Series in Information Processing, v. 1, Konstanz: ETH Series in Information Processing, v. 1, Konstanz:
Hartung-Gorre Verlag , 1992. Hartung-Gorre Verlag, 1992.
[PKCS1] RSA Laboratories, "PKCS #1: RSA Encryption Standard [PKCS1] RSA Laboratories, "PKCS #1: RSA Encryption Standard
version 1.5", November 1993. version 1.5", November 1993.
[PKCS6] RSA Laboratories, "PKCS #6: RSA Extended Certificate [PKCS6] RSA Laboratories, "PKCS #6: RSA Extended Certificate
Syntax Standard version 1.5", November 1993. Syntax Standard version 1.5", November 1993.
[PKCS7] RSA Laboratories, "PKCS #7: RSA Cryptographic Message [PKCS7] RSA Laboratories, "PKCS #7: RSA Cryptographic Message
Syntax Standard version 1.5", November 1993. Syntax Standard version 1.5", November 1993.
[RSA] Rivest, R., Shamir, A., and L. Adleman, "A Method for [RSA] Rivest, R., Shamir, A., and L. Adleman, "A Method for
Obtaining Digital Signatures and Public-Key Obtaining Digital Signatures and Public-Key
Cryptosystems", Communications of the ACM v. 21, n. 2 pp. Cryptosystems", Communications of the ACM v. 21, n. 2 pp.
120-126., February 1978. 120-126., February 1978.
[SCH] Schneier, B., "Applied Cryptography: Protocols, [SCH] Schneier, B., "Applied Cryptography: Protocols,
Algorithms, and Source Code in C", John Wiley & Sons , Algorithms, and Source Code in C", John Wiley & Sons,
1994. 1994.
[SHA] NIST FIPS PUB 180-1, "Secure Hash Standard", May 1994. [SHA] NIST FIPS PUB 180-1, "Secure Hash Standard", May 1994.
National Institute of Standards and Technology, U.S. National Institute of Standards and Technology, U.S.
Department of Commerce, DRAFT Department of Commerce, DRAFT
[X509] CCITT, "The Directory - Authentication Framework", [X509] CCITT, "The Directory - Authentication Framework",
Recommendation X.509 , 1988. Recommendation X.509 , 1988.
[RSADSI] RSA Data Security, Inc., "Unpublished works". [RSADSI] RSA Data Security, Inc., "Unpublished works".
Appendix A. Protocol constant values Appendix A. Protocol Constant Values
This section describes protocol types and constants. This section describes protocol types and constants.
A.1. Record layer A.1. Record Layer
struct { struct {
uint8 major, minor; uint8 major, minor;
} ProtocolVersion; } ProtocolVersion;
ProtocolVersion version = { 3,0 }; ProtocolVersion version = { 3,0 };
enum { enum {
change_cipher_spec(20), alert(21), handshake(22), change_cipher_spec(20), alert(21), handshake(22),
application_data(23), (255) application_data(23), (255)
} ContentType; } ContentType;
skipping to change at page 43, line 5 skipping to change at page 43, line 9
opaque MAC[CipherSpec.hash_size]; opaque MAC[CipherSpec.hash_size];
} GenericStreamCipher; } GenericStreamCipher;
block-ciphered struct { block-ciphered struct {
opaque content[SSLCompressed.length]; opaque content[SSLCompressed.length];
opaque MAC[CipherSpec.hash_size]; opaque MAC[CipherSpec.hash_size];
uint8 padding[GenericBlockCipher.padding_length]; uint8 padding[GenericBlockCipher.padding_length];
uint8 padding_length; uint8 padding_length;
} GenericBlockCipher; } GenericBlockCipher;
A.2. Change cipher specs message A.2. Change Cipher Specs Message
struct { struct {
enum { change_cipher_spec(1), (255) } type; enum { change_cipher_spec(1), (255) } type;
} ChangeCipherSpec; } ChangeCipherSpec;
A.3. Alert messages A.3. Alert Messages
enum { warning(1), fatal(2), (255) } AlertLevel; enum { warning(1), fatal(2), (255) } AlertLevel;
enum { enum {
close_notify(0), close_notify(0),
unexpected_message(10), unexpected_message(10),
bad_record_mac(20), bad_record_mac(20),
decompression_failure(30), decompression_failure(30),
handshake_failure(40), handshake_failure(40),
no_certificate(41), no_certificate(41),
skipping to change at page 43, line 36 skipping to change at page 44, line 5
certificate_unknown(46), certificate_unknown(46),
illegal_parameter (47), illegal_parameter (47),
(255) (255)
} AlertDescription; } AlertDescription;
struct { struct {
AlertLevel level; AlertLevel level;
AlertDescription description; AlertDescription description;
} Alert; } Alert;
A.4. Handshake protocol A.4. Handshake Protocol
enum { enum {
hello_request(0), client_hello(1), server_hello(2), hello_request(0), client_hello(1), server_hello(2),
certificate(11), server_key_exchange (12), certificate(11), server_key_exchange (12),
certificate_request(13), server_done(14), certificate_request(13), server_done(14),
certificate_verify(15), client_key_exchange(16), certificate_verify(15), client_key_exchange(16),
finished(20), (255) finished(20), (255)
} HandshakeType; } HandshakeType;
struct { struct {
HandshakeType msg_type; HandshakeType msg_type;
skipping to change at page 44, line 29 skipping to change at page 44, line 32
case certificate: Certificate; case certificate: Certificate;
case server_key_exchange: ServerKeyExchange; case server_key_exchange: ServerKeyExchange;
case certificate_request: CertificateRequest; case certificate_request: CertificateRequest;
case server_done: ServerHelloDone; case server_done: ServerHelloDone;
case certificate_verify: CertificateVerify; case certificate_verify: CertificateVerify;
case client_key_exchange: ClientKeyExchange; case client_key_exchange: ClientKeyExchange;
case finished: Finished; case finished: Finished;
} body; } body;
} Handshake; } Handshake;
A.4.1. Hello messages A.4.1. Hello Messages
struct { } HelloRequest; struct { } HelloRequest;
struct { struct {
uint32 gmt_unix_time; uint32 gmt_unix_time;
opaque random_bytes[28]; opaque random_bytes[28];
} Random; } Random;
opaque SessionID<0..32>; opaque SessionID<0..32>;
uint8 CipherSuite[2]; uint8 CipherSuite[2];
skipping to change at page 45, line 33 skipping to change at page 45, line 15
} ClientHello; } ClientHello;
struct { struct {
ProtocolVersion server_version; ProtocolVersion server_version;
Random random; Random random;
SessionID session_id; SessionID session_id;
CipherSuite cipher_suite; CipherSuite cipher_suite;
CompressionMethod compression_method; CompressionMethod compression_method;
} ServerHello; } ServerHello;
A.4.2. Server authentication and key exchange messages A.4.2. Server Authentication and Key Exchange Messages
opaque ASN.1Cert<2^24-1>; opaque ASN.1Cert<2^24-1>;
struct { struct {
ASN.1Cert certificate_list<1..2^24-1>; ASN.1Cert certificate_list<1..2^24-1>;
} Certificate; } Certificate;
enum { rsa, diffie_hellman, fortezza_kea } KeyExchangeAlgorithm; enum { rsa, diffie_hellman, fortezza_kea } KeyExchangeAlgorithm;
struct { struct {
skipping to change at page 47, line 4 skipping to change at page 46, line 29
DSS_fixed_DH(4), RSA_ephemeral_DH(5), DSS_ephemeral_DH(6), DSS_fixed_DH(4), RSA_ephemeral_DH(5), DSS_ephemeral_DH(6),
FORTEZZA_MISSI(20), (255) FORTEZZA_MISSI(20), (255)
} CertificateType; } CertificateType;
opaque DistinguishedName<1..2^16-1>; opaque DistinguishedName<1..2^16-1>;
struct { struct {
CertificateType certificate_types<1..2^8-1>; CertificateType certificate_types<1..2^8-1>;
DistinguishedName certificate_authorities<3..2^16-1>; DistinguishedName certificate_authorities<3..2^16-1>;
} CertificateRequest; } CertificateRequest;
struct { } ServerHelloDone; struct { } ServerHelloDone;
A.5. Client authentication and key exchange messages A.5. Client Authentication and Key Exchange Messages
struct { struct {
select (KeyExchangeAlgorithm) { select (KeyExchangeAlgorithm) {
case rsa: EncryptedPreMasterSecret; case rsa: EncryptedPreMasterSecret;
case diffie_hellman: DiffieHellmanClientPublicValue; case diffie_hellman: DiffieHellmanClientPublicValue;
case fortezza_kea: FortezzaKeys; case fortezza_kea: FortezzaKeys;
} exchange_keys; } exchange_keys;
} ClientKeyExchange; } ClientKeyExchange;
struct { struct {
skipping to change at page 48, line 5 skipping to change at page 47, line 29
select (PublicValueEncoding) { select (PublicValueEncoding) {
case implicit: struct {}; case implicit: struct {};
case explicit: opaque DH_Yc<1..2^16-1>; case explicit: opaque DH_Yc<1..2^16-1>;
} dh_public; } dh_public;
} ClientDiffieHellmanPublic; } ClientDiffieHellmanPublic;
struct { struct {
Signature signature; Signature signature;
} CertificateVerify; } CertificateVerify;
A.5.1. Handshake finalization message A.5.1. Handshake Finalization Message
struct { struct {
opaque md5_hash[16]; opaque md5_hash[16];
opaque sha_hash[20]; opaque sha_hash[20];
} Finished; } Finished;
A.6. The CipherSuite A.6. The CipherSuite
The following values define the CipherSuite codes used in the client The following values define the CipherSuite codes used in the client
hello and server hello messages. hello and server hello messages.
A CipherSuite defines a cipher specifications supported in SSL A CipherSuite defines a cipher specifications supported in SSL
Version 3.0. version 3.0.
CipherSuite SSL_NULL_WITH_NULL_NULL = { 0x00,0x00 }; CipherSuite SSL_NULL_WITH_NULL_NULL = { 0x00,0x00 };
The following CipherSuite definitions require that the server provide The following CipherSuite definitions require that the server provide
an RSA certificate that can be used for key exchange. The server may an RSA certificate that can be used for key exchange. The server may
request either an RSA or a DSS signature-capable certificate in the request either an RSA or a DSS signature-capable certificate in the
certificate request message. certificate request message.
CipherSuite SSL_RSA_WITH_NULL_MD5 = { 0x00,0x01 }; CipherSuite SSL_RSA_WITH_NULL_MD5 = { 0x00,0x01 };
CipherSuite SSL_RSA_WITH_NULL_SHA = { 0x00,0x02 }; CipherSuite SSL_RSA_WITH_NULL_SHA = { 0x00,0x02 };
skipping to change at page 50, line 26 skipping to change at page 50, line 7
MACAlgorithm mac_algorithm; MACAlgorithm mac_algorithm;
CipherType cipher_type; CipherType cipher_type;
IsExportable is_exportable IsExportable is_exportable
uint8 hash_size; uint8 hash_size;
uint8 key_material; uint8 key_material;
uint8 IV_size; uint8 IV_size;
} CipherSpec; } CipherSpec;
Appendix B. Glossary Appendix B. Glossary
application protocol An application protocol is a protocol that application protocol: An application protocol is a protocol that
normally layers directly on top of the transport layer (e.g., normally layers directly on top of the transport layer (e.g.,
TCP/IP). Examples include HTTP, TELNET, FTP, and SMTP. TCP/IP [RFC0793]/[RFC0791]). Examples include HTTP [RFC1945],
TELNET [RFC0959], FTP [RFC0854], and SMTP.
asymetric cipher See public key cryptography. asymmetric cipher: See public key cryptography.
authentication Authentication is the ability of one entity to authentication: Authentication is the ability of one entity to
determine the identity of another entity. determine the identity of another entity.
block cipher A block cipher is an algorithm that operates on block cipher: A block cipher is an algorithm that operates on
plaintext in groups of bits, called blocks. 64 bits is a typical plaintext in groups of bits, called blocks. 64 bits is a typical
block size. block size.
bulk cipher A symmetric encryption algorithm used to encrypt large bulk cipher: A symmetric encryption algorithm used to encrypt large
quantities of data. quantities of data.
cipher block chaining Mode (CBC) CBC is a mode in which every cipher block chaining (CBC) mode: CBC is a mode in which every
plaintext block encrypted with the block cipher is first plaintext block encrypted with the block cipher is first
exclusive-ORed with the previous ciphertext block (or, in the case exclusive-ORed with the previous ciphertext block (or, in the case
of the first block, with the initialization vector). of the first block, with the initialization vector).
certificate As part of the X.509 protocol (a.k.a. ISO certificate: As part of the X.509 protocol (a.k.a. ISO
Authentication framework), certificates are assigned by a trusted Authentication framework), certificates are assigned by a trusted
Certificate Authority and provide verification of a party's certificate authority and provide verification of a party's
identity and may also supply its public key. identity and may also supply its public key.
client The application entity that initiates a connection to a client: The application entity that initiates a connection to a
server. server.
client write key The key used to encrypt data written by the client. client write key: The key used to encrypt data written by the
client.
client write MAC secret The secret data used to authenticate data client write MAC secret: The secret data used to authenticate data
written by the client. written by the client.
connection A connection is a transport (in the OSI layering model connection: A connection is a transport (in the OSI layering model
definition) that provides a suitable type of service. For SSL, definition) that provides a suitable type of service. For SSL,
such connections are peer to peer relationships. The connections such connections are peer-to-peer relationships. The connections
are transient. Every connection is associated with one session. are transient. Every connection is associated with one session.
Data Encryption Standard (DES) DES is a very widely used symmetric Data Encryption Standard (DES): DES is a very widely used symmetric
encryption algorithm. DES is a block cipher. encryption algorithm. DES is a block cipher [DES] [3DES].
Digital Signature Standard (DSS) A standard for digital signing, Digital Signature Standard: (DSS) A standard for digital signing,
including the Digital Signing Algorithm, approved by the National including the Digital Signature Algorithm, approved by the
Institute of Standards and Technology, defined in NIST FIPS PUB National Institute of Standards and Technology, defined in NIST
186, "Digital Signature Standard," published May, 1994 by the U.S. FIPS PUB 186, "Digital Signature Standard," published May, 1994 by
Dept. of Commerce. the U.S. Dept. of Commerce.
digital signatures Digital signatures utilize public key digital signatures: Digital signatures utilize public key
cryptography and one-way hash functions to produce a signature of cryptography and one-way hash functions to produce a signature of
the data that can be authenticated, and is difficult to forge or the data that can be authenticated, and is difficult to forge or
repudiate. repudiate.
FORTEZZA A PCMCIA card that provides both encryption and digital FORTEZZA: A PCMCIA card that provides both encryption and digital
signing. signing.
handshake An initial negotiation between client and server that handshake: An initial negotiation between client and server that
establishes the parameters of their transactions. establishes the parameters of their transactions.
Initialization Vector (IV) When a block cipher is used in CBC mode, Initialization Vector (IV): When a block cipher is used in CBC mode,
the initialization vector is exclusive-ORed with the first the initialization vector is exclusive-ORed with the first
plaintext block prior to encryption. plaintext block prior to encryption.
IDEA A 64-bit block cipher designed by Xuejia Lai and James Massey. IDEA: A 64-bit block cipher designed by Xuejia Lai and James Massey
[IDEA].
Message Authentication Code (MAC) A Message Authentication Code is a Message Authentication Code (MAC): A Message Authentication Code is
one-way hash computed from a message and some secret data. Its a one-way hash computed from a message and some secret data. Its
purpose is to detect if the message has been altered. purpose is to detect if the message has been altered.
master secret Secure secret data used for generating encryption master secret: Secure secret data used for generating encryption
keys, MAC secrets, and IVs. keys, MAC secrets, and IVs.
MD5 MD5 [RFC1321] is a secure hashing function that converts an MD5: MD5 [RFC1321] is a secure hashing function that converts an
arbitrarily long data stream into a digest of fixed size. arbitrarily long data stream into a digest of fixed size.
public key cryptography A class of cryptographic techniques public key cryptography: A class of cryptographic techniques
employing two-key ciphers. Messages encrypted with the public key employing two-key ciphers. Messages encrypted with the public key
can only be decrypted with the associated private key. can only be decrypted with the associated private key.
Conversely, messages signed with the private key can be verified Conversely, messages signed with the private key can be verified
with the public key. with the public key.
one-way hash function A one-way transformation that converts an one-way hash function: A one-way transformation that converts an
arbitrary amount of data into a fixed-length hash. It is arbitrary amount of data into a fixed-length hash. It is
computation- ally hard to reverse the transformation or to find computationally hard to reverse the transformation or to find
collisions. MD5 and SHA are examples of one-way hash functions. collisions. MD5 and SHA are examples of one-way hash functions.
RC2, RC4 Proprietary bulk ciphers from RSA Data Security, Inc. RC2, RC4: Proprietary bulk ciphers from RSA Data Security, Inc.
(There is no good reference to these as they are unpublished (There is no good reference to these as they are unpublished
works; however, see [RSADSI]). RC2 is block cipher and RC4 is a works; however, see [RSADSI]). RC2 is a block cipher and RC4 is a
stream cipher. stream cipher.
RSA A very widely used public-key algorithm that can be used for RSA: A very widely used public key algorithm that can be used for
either encryption or digital signing. either encryption or digital signing.
salt Non-secret random data used to make export encryption keys salt: Non-secret random data used to make export encryption keys
resist precomputation attacks. resist precomputation attacks.
server The server is the application entity that responds to server: The server is the application entity that responds to
requests for connections from clients. The server is passive, requests for connections from clients. The server is passive,
waiting for requests from clients. waiting for requests from clients.
session A SSL session is an association between a client and a session: An SSL session is an association between a client and a
server. Sessions are created by the handshake protocol. Sessions server. Sessions are created by the handshake protocol. Sessions
define a set of cryptographic security parameters, which can be define a set of cryptographic security parameters, which can be
shared among multiple connections. Sessions are used to avoid the shared among multiple connections. Sessions are used to avoid the
expensive negotiation of new security parameters for each expensive negotiation of new security parameters for each
connection. connection.
session identifier A session identifier is a value generated by a session identifier: A session identifier is a value generated by a
server that identifies a particular session. server that identifies a particular session.
server write key The key used to encrypt data written by the server. server write key: The key used to encrypt data written by the
server.
server write MAC secret The secret data used to authenticate data server write MAC secret: The secret data used to authenticate data
written by the server. written by the server.
SHA The Secure Hash Algorithm is defined in FIPS PUB 180-1. It SHA: The Secure Hash Algorithm is defined in FIPS PUB 180-1. It
produces a 20-byte output [SHA]. produces a 20-byte output [SHA].
stream cipher An encryption algorithm that converts a key into a stream cipher: An encryption algorithm that converts a key into a
cryptographically-strong keystream, which is then exclusive-ORed cryptographically strong keystream, which is then exclusive-ORed
with the plaintext. with the plaintext.
symmetric cipher See bulk cipher. symmetric cipher: See bulk cipher.
Appendix C. CipherSuite definitions Appendix C. CipherSuite Definitions
CipherSuite Is Key Cipher Hash CipherSuite Is Key Cipher Hash
Exportable Exchange Exportable Exchange
SSL_NULL_WITH_NULL_NULL * NULL NULL NULL SSL_NULL_WITH_NULL_NULL * NULL NULL NULL
SSL_RSA_WITH_NULL_MD5 * RSA NULL MD5 SSL_RSA_WITH_NULL_MD5 * RSA NULL MD5
SSL_RSA_WITH_NULL_SHA * RSA NULL SHA SSL_RSA_WITH_NULL_SHA * RSA NULL SHA
SSL_RSA_EXPORT_WITH_RC4_40_MD5 * RSA_EXPORT RC4_40 MD5 SSL_RSA_EXPORT_WITH_RC4_40_MD5 * RSA_EXPORT RC4_40 MD5
SSL_RSA_WITH_RC4_128_MD5 RSA RC4_128 MD5 SSL_RSA_WITH_RC4_128_MD5 RSA RC4_128 MD5
SSL_RSA_WITH_RC4_128_SHA RSA RC4_128 SHA SSL_RSA_WITH_RC4_128_SHA RSA RC4_128 SHA
skipping to change at page 54, line 5 skipping to change at page 54, line 5
SSL_DHE_RSA_WITH_3DES_EDE_CBC_SHA DHE_RSA 3DES_EDE_CBC SHA SSL_DHE_RSA_WITH_3DES_EDE_CBC_SHA DHE_RSA 3DES_EDE_CBC SHA
SSL_DH_anon_EXPORT_WITH_RC4_40_MD5 * DH_anon_EXPORT RC4_40 MD5 SSL_DH_anon_EXPORT_WITH_RC4_40_MD5 * DH_anon_EXPORT RC4_40 MD5
SSL_DH_anon_WITH_RC4_128_MD5 DH_anon RC4_128 MD5 SSL_DH_anon_WITH_RC4_128_MD5 DH_anon RC4_128 MD5
SSL_DH_anon_EXPORT_WITH_DES40_CBC_SHA DH_anon DES40_CBC SHA SSL_DH_anon_EXPORT_WITH_DES40_CBC_SHA DH_anon DES40_CBC SHA
SSL_DH_anon_WITH_DES_CBC_SHA DH_anon DES_CBC SHA SSL_DH_anon_WITH_DES_CBC_SHA DH_anon DES_CBC SHA
SSL_DH_anon_WITH_3DES_EDE_CBC_SHA DH_anon 3DES_EDE_CBC SHA SSL_DH_anon_WITH_3DES_EDE_CBC_SHA DH_anon 3DES_EDE_CBC SHA
SSL_FORTEZZA_KEA_WITH_NULL_SHA FORTEZZA_KEA NULL SHA SSL_FORTEZZA_KEA_WITH_NULL_SHA FORTEZZA_KEA NULL SHA
SSL_FORTEZZA_KEA_WITH_FORTEZZA_CBC_SHA FORTEZZA_KEA FORTEZZA_CBC SHA SSL_FORTEZZA_KEA_WITH_FORTEZZA_CBC_SHA FORTEZZA_KEA FORTEZZA_CBC SHA
SSL_FORTEZZA_KEA_WITH_RC4_128_SHA FORTEZZA_KEA RC4_128 SHA SSL_FORTEZZA_KEA_WITH_RC4_128_SHA FORTEZZA_KEA RC4_128 SHA
+----------------+------------------------------+-------------------+ +----------------+------------------------------+-------------------+
| Key Exchange | Description | Key size limit | | Key Exchange | Description | Key Size Limit |
| Algorithm | | | | Algorithm | | |
+----------------+------------------------------+-------------------+ +----------------+------------------------------+-------------------+
| DHE_DSS | Ephemeral DH with DSS | None | | DHE_DSS | Ephemeral DH with DSS | None |
| | signatures | | | | signatures | |
| DHE_DSS_EXPORT | Ephemeral DH with DSS | DH = 512 bits | | DHE_DSS_EXPORT | Ephemeral DH with DSS | DH = 512 bits |
| | signatures | | | | signatures | |
| DHE_RSA | Ephemeral DH with RSA | None | | DHE_RSA | Ephemeral DH with RSA | None |
| | signatures | | | | signatures | |
| DHE_RSA_EXPORT | Ephemeral DH with RSA | DH = 512 bits, | | DHE_RSA_EXPORT | Ephemeral DH with RSA | DH = 512 bits, |
| | signatures | RSA = none | | | signatures | RSA = none |
skipping to change at page 54, line 35 skipping to change at page 54, line 35
| | certificates | RSA = none | | | certificates | RSA = none |
| FORTEZZA_KEA | FORTEZZA KEA. Details | N/A | | FORTEZZA_KEA | FORTEZZA KEA. Details | N/A |
| | unpublished | | | | unpublished | |
| NULL | No key exchange | N/A | | NULL | No key exchange | N/A |
| RSA | RSA key exchange | None | | RSA | RSA key exchange | None |
| RSA_EXPORT | RSA key exchange | RSA = 512 bits | | RSA_EXPORT | RSA key exchange | RSA = 512 bits |
+----------------+------------------------------+-------------------+ +----------------+------------------------------+-------------------+
Table 1 Table 1
Key size limit The key size limit gives the size of the largest Key size limit: The key size limit gives the size of the largest
public key that can be legally used for encryption in cipher public key that can be legally used for encryption in cipher
suites that are exportable. suites that are exportable.
+--------------+--------+-----+-------+-------+-------+------+------+ +--------------+--------+-----+-------+-------+-------+------+------+
| Cipher | Cipher | IsE | Key | Exp. | Effec | IV | Bloc | | Cipher | Cipher | IsE | Key | Exp. | Effec | IV | Bloc |
| | Type | xpo | Mater | Key | tive | Size | k | | | Type | xpo | Mater | Key | tive | Size | k |
| | | rta | ial | Mater | Key | | Size | | | | rta | ial | Mater | Key | | Size |
| | | ble | | ial | Bits | | | | | | ble | | ial | Bits | | |
+--------------+--------+-----+-------+-------+-------+------+------+ +--------------+--------+-----+-------+-------+-------+------+------+
| NULL | Stream | * | 0 | 0 | 0 | 0 | N/A | | NULL | Stream | * | 0 | 0 | 0 | 0 | N/A |
skipping to change at page 55, line 23 skipping to change at page 55, line 23
| | | | (**) | (**) | (**) | (**) | | | | | | (**) | (**) | (**) | (**) | |
| IDEA_CBC | Block | | 16 | 16 | 128 | 8 | 8 | | IDEA_CBC | Block | | 16 | 16 | 128 | 8 | 8 |
| RC2_CBC_40 | Block | * | 5 | 16 | 40 | 8 | 8 | | RC2_CBC_40 | Block | * | 5 | 16 | 40 | 8 | 8 |
| RC4_40 | Stream | * | 5 | 16 | 40 | 0 | N/A | | RC4_40 | Stream | * | 5 | 16 | 40 | 0 | N/A |
| RC4_128 | Stream | | 16 | 16 | 128 | 0 | N/A | | RC4_128 | Stream | | 16 | 16 | 128 | 0 | N/A |
| DES40_CBC | Block | * | 5 | 8 | 40 | 8 | 8 | | DES40_CBC | Block | * | 5 | 8 | 40 | 8 | 8 |
| DES_CBC | Block | | 8 | 8 | 56 | 8 | 8 | | DES_CBC | Block | | 8 | 8 | 56 | 8 | 8 |
| 3DES_EDE_CBC | Block | | 24 | 24 | 168 | 8 | 8 | | 3DES_EDE_CBC | Block | | 24 | 24 | 168 | 8 | 8 |
+--------------+--------+-----+-------+-------+-------+------+------+ +--------------+--------+-----+-------+-------+-------+------+------+
* Indicates IsExportable is true. ** FORTEZZA uses its own key and IV * Indicates IsExportable is true.
generation algorithms. ** FORTEZZA uses its own key and IV generation algorithms.
Table 2 Table 2
Key Material The number of bytes from the key_block that are used Key Material: The number of bytes from the key_block that are used
for generating the write keys. for generating the write keys.
Expanded Key Material The number of bytes actually fed into the Expanded Key Material: The number of bytes actually fed into the
encryption algorithm. encryption algorithm.
Effective Key Bits How much entropy material is in the key material Effective Key Bits: How much entropy material is in the key material
being fed into the encryption routines. being fed into the encryption routines.
+---------------+-----------+--------------+ +---------------+-----------+--------------+
| Hash function | Hash Size | Padding Size | | Hash Function | Hash Size | Padding Size |
+---------------+-----------+--------------+ +---------------+-----------+--------------+
| NULL | 0 | 0 | | NULL | 0 | 0 |
| MD5 | 16 | 48 | | MD5 | 16 | 48 |
| SHA | 20 | 40 | | SHA | 20 | 40 |
+---------------+-----------+--------------+ +---------------+-----------+--------------+
Table 3 Table 3
Appendix D. Implementation Notes Appendix D. Implementation Notes
The SSL protocol cannot prevent many common security mistakes. This The SSL protocol cannot prevent many common security mistakes. This
section provides several recommendations to assist implementers. section provides several recommendations to assist implementers.
D.1. Temporary RSA keys D.1. Temporary RSA Keys
US Export restrictions limit RSA keys used for encryption to 512 US export restrictions limit RSA keys used for encryption to 512
bits, but do not place any limit on lengths of RSA keys used for bits, but do not place any limit on lengths of RSA keys used for
signing operations. Certificates often need to be larger than 512 signing operations. Certificates often need to be larger than 512
bits, since 512-bit RSA keys are not secure enough for high-value bits, since 512-bit RSA keys are not secure enough for high-value
transactions or for applications requiring long-term security. Some transactions or for applications requiring long-term security. Some
certificates are also designated signing-only, in which case they certificates are also designated signing-only, in which case they
cannot be used for key exchange. cannot be used for key exchange.
When the public key in the certificate cannot be used for encryption, When the public key in the certificate cannot be used for encryption,
the server signs a temporary RSA key, which is then exchanged. In the server signs a temporary RSA key, which is then exchanged. In
exportable applications, the temporary RSA key should be the maximum exportable applications, the temporary RSA key should be the maximum
skipping to change at page 56, line 32 skipping to change at page 56, line 37
Note that while it is acceptable to use the same temporary key for Note that while it is acceptable to use the same temporary key for
multiple transactions, it must be signed each time it is used. multiple transactions, it must be signed each time it is used.
RSA key generation is a time-consuming process. In many cases, a RSA key generation is a time-consuming process. In many cases, a
low-priority process can be assigned the task of key generation. low-priority process can be assigned the task of key generation.
Whenever a new key is completed, the existing temporary key can be Whenever a new key is completed, the existing temporary key can be
replaced with the new one. replaced with the new one.
D.2. Random Number Generation and Seeding D.2. Random Number Generation and Seeding
SSL requires a cryptographically-secure pseudorandom number generator SSL requires a cryptographically secure pseudorandom number generator
(PRNG). Care must be taken in designing and seeding PRNGs. PRNGs (PRNG). Care must be taken in designing and seeding PRNGs. PRNGs
based on secure hash operations, most notably MD5 and/or SHA, are based on secure hash operations, most notably MD5 and/or SHA, are
acceptable, but cannot provide more security than the size of the acceptable, but cannot provide more security than the size of the
random number generator state. (For example, MD5-based PRNGs usually random number generator state. (For example, MD5-based PRNGs usually
provide 128 bits of state.) provide 128 bits of state.)
To estimate the amount of seed material being produced, add the To estimate the amount of seed material being produced, add the
number of bits of unpredictable information in each seed byte. For number of bits of unpredictable information in each seed byte. For
example, keystroke timing values taken from a PC- compatible's 18.2 example, keystroke timing values taken from a PC-compatible's 18.2 Hz
Hz timer provide 1 or 2 secure bits each, even though the total size timer provide 1 or 2 secure bits each, even though the total size of
of the counter value is 16 bits or more. To seed a 128-bit PRNG, one the counter value is 16 bits or more. To seed a 128-bit PRNG, one
would thus require approximately 100 such timer values. would thus require approximately 100 such timer values.
Note: The seeding functions in RSAREF and versions of BSAFE prior to Note: The seeding functions in RSAREF and versions of BSAFE prior to
3.0 are order-independent. For example, if 1000 seed bits are 3.0 are order independent. For example, if 1000 seed bits are
supplied, one at a time, in 1000 separate calls to the seed function, supplied, one at a time, in 1000 separate calls to the seed function,
the PRNG will end up in a state which depends only on the number of 0 the PRNG will end up in a state that depends only on the number of 0
or 1 seed bits in the seed data (i.e., there are 1001 possible final or 1 seed bits in the seed data (i.e., there are 1001 possible final
states). Applications using BSAFE or RSAREF must take extra care to states). Applications using BSAFE or RSAREF must take extra care to
ensure proper seeding. ensure proper seeding.
D.3. Certificates and authentication D.3. Certificates and Authentication
Implementations are responsible for verifying the integrity of Implementations are responsible for verifying the integrity of
certificates and should generally support certificate revocation certificates and should generally support certificate revocation
messages. Certificates should always be verified to ensure proper messages. Certificates should always be verified to ensure proper
signing by a trusted Certificate Authority (CA). The selection and signing by a trusted certificate authority (CA). The selection and
addition of trusted CAs should be done very carefully. Users should addition of trusted CAs should be done very carefully. Users should
be able to view information about the certificate and root CA. be able to view information about the certificate and root CA.
D.4. CipherSuites D.4. CipherSuites
SSL supports a range of key sizes and security levels, including some SSL supports a range of key sizes and security levels, including some
which provide no or minimal security. A proper implementation will that provide no or minimal security. A proper implementation will
probably not support many cipher suites. For example, 40-bit probably not support many cipher suites. For example, 40-bit
encryption is easily broken, so implementations requiring strong encryption is easily broken, so implementations requiring strong
security should not allow 40-bit keys. Similarly, anonymous Diffie- security should not allow 40-bit keys. Similarly, anonymous Diffie-
Hellman is strongly discouraged because it cannot prevent man-in-the- Hellman is strongly discouraged because it cannot prevent man-in-the-
middle attacks. Applications should also enforce minimum and maximum middle attacks. Applications should also enforce minimum and maximum
key sizes. For example, certificate chains containing 512-bit RSA key sizes. For example, certificate chains containing 512-bit RSA
keys or signatures are not appropriate for high-security keys or signatures are not appropriate for high-security
applications. applications.
D.5. FORTEZZA D.5. FORTEZZA
This section describes implementation details for ciphersuites that This section describes implementation details for cipher suites that
make use of the FORTEZZA hardware encryption system. make use of the FORTEZZA hardware encryption system.
D.5.1. Notes on use of FORTEZZA hardware D.5.1. Notes on Use of FORTEZZA Hardware
A complete explanation of all issues regarding the use of FORTEZZA A complete explanation of all issues regarding the use of FORTEZZA
hardware is outside the scope of this document. However, there are a hardware is outside the scope of this document. However, there are a
few special requirements of SSL that deserve mention. few special requirements of SSL that deserve mention.
Because SSL is a full duplex protocol, two crypto states must be Because SSL is a full duplex protocol, two crypto states must be
maintained, one for reading and one for writing. There are also a maintained, one for reading and one for writing. There are also a
number of circumstances which can result in the crypto state in the number of circumstances that can result in the crypto state in the
FORTEZZA card being lost. For these reasons, it's recommended that FORTEZZA card being lost. For these reasons, it's recommended that
the current crypto state be saved after processing a record, and the current crypto state be saved after processing a record, and
loaded before processing the next. loaded before processing the next.
After the client generates the TEK, it also generates two MEKs, for After the client generates the TEK, it also generates two message
one for reading and one for writing. After generating each of these encryption keys (MEKs), one for reading and one for writing. After
keys, the client must generate a corresponding IV and then save the generating each of these keys, the client must generate a
crypto state. The client also uses the TEK to generate an IV and corresponding IV and then save the crypto state. The client also
encrypt the premaster secret. All three IVs are sent to the server, uses the TEK to generate an IV and encrypt the premaster secret. All
along with the wrapped keys and the encrypted premaster secret in the three IVs are sent to the server, along with the wrapped keys and the
client key exchange message. At this point, the TEK is no longer encrypted premaster secret in the client key exchange message. At
needed, and may be discarded. this point, the TEK is no longer needed, and may be discarded.
On the server side, the server uses the master IV and the TEK to On the server side, the server uses the master IV and the TEK to
decrypt the premaster secret. It also loads the wrapped MEKs into decrypt the premaster secret. It also loads the wrapped MEKs into
the card. The server loads both IVs to verify that the IVs match the the card. The server loads both IVs to verify that the IVs match the
keys. However, since the card is unable to encrypt after loading an keys. However, since the card is unable to encrypt after loading an
IV, the server must generate a new IV for the server write key. This IV, the server must generate a new IV for the server write key. This
IV is discarded. IV is discarded.
When encrypting the first encrypted record (and only that record), When encrypting the first encrypted record (and only that record),
the server adds 8 bytes of random data to the beginning of the the server adds 8 bytes of random data to the beginning of the
fragment. These 8 bytes are discarded by the client after fragment. These 8 bytes are discarded by the client after
decryption. The purpose of this is to synchronize the state on the decryption. The purpose of this is to synchronize the state on the
client and server resulting from the different IVs. client and server resulting from the different IVs.
D.5.2. FORTEZZA Ciphersuites D.5.2. FORTEZZA Cipher Suites
5) FORTEZZA_NULL_WITH_NULL_SHA: Uses the full FORTEZZA key exchange, 5) FORTEZZA_NULL_WITH_NULL_SHA: Uses the full FORTEZZA key exchange,
including sending server and client write keys and iv's. including sending server and client write keys and IVs.
D.5.3. FORTEZZA Session resumption D.5.3. FORTEZZA Session Resumption
There are two possibilities for FORTEZZA session restart: 1) Never There are two possibilities for FORTEZZA session restart: 1) Never
restart a FORTEZZA session. 2) Restart a session with the previously restart a FORTEZZA session. 2) Restart a session with the previously
negotiated keys and iv's. negotiated keys and IVs.
Never restarting a FORTEZZA session: Never restarting a FORTEZZA session:
Clients who never restart FORTEZZA sessions should never send Session Clients who never restart FORTEZZA sessions should never send session
ID's which were previously used in a FORTEZZA session as part of the IDs that were previously used in a FORTEZZA session as part of the
ClientHello. Servers who never restart FORTEZZA sessions should ClientHello. Servers who never restart FORTEZZA sessions should
never send a previous session id on the ServerHello if the negotiated never send a previous session id on the ServerHello if the negotiated
session is FORTEZZA. session is FORTEZZA.
Restart a session: Restart a session:
You cannot restart FORTEZZA on a session which has never done a You cannot restart FORTEZZA on a session that has never done a
complete FORTEZZA key exchange (That is you cannot restart FORTEZZA complete FORTEZZA key exchange (that is, you cannot restart FORTEZZA
if the session was an RSA/RC4 session renegotiated for FORTEZZA). If if the session was an RSA/RC4 session renegotiated for FORTEZZA). If
you wish to restart a FORTEZZA session, you must save the MEKs and you wish to restart a FORTEZZA session, you must save the MEKs and
IVs from the initial key exchange for this session and reuse them for IVs from the initial key exchange for this session and reuse them for
any new connections on that session. This is not recommended, but it any new connections on that session. This is not recommended, but it
is possible. is possible.
Appendix E. Version 2.0 Backward Compatibility Appendix E. Version 2.0 Backward Compatibility
Version 3.0 clients that support Version 2.0 servers must send Version 3.0 clients that support version 2.0 servers must send
Version 2.0 client hello messages [SSL-2]. Version 3.0 servers version 2.0 client hello messages [SSL-2]. Version 3.0 servers
should accept either client hello format. The only deviations from should accept either client hello format. The only deviations from
the Version 2.0 specification are the ability to specify a version the version 2.0 specification are the ability to specify a version
with a value of three and the support for more ciphering types in the with a value of three and the support for more ciphering types in the
CipherSpec. CipherSpec.
Warning: The ability to send Version 2.0 client hello messages will Warning: The ability to send version 2.0 client hello messages will
be phased out with all due haste. Implementers should make every be phased out with all due haste. Implementers should make every
effort to move forward as quickly as possible. Version 3.0 provides effort to move forward as quickly as possible. Version 3.0 provides
better mechanisms for transitioning to newer versions. better mechanisms for transitioning to newer versions.
The following cipher specifications are carryovers from SSL Version The following cipher specifications are carryovers from SSL version
2.0. These are assumed to use RSA for key exchange and 2.0. These are assumed to use RSA for key exchange and
authentication. authentication.
V2CipherSpec SSL_RC4_128_WITH_MD5 = { 0x01,0x00,0x80 }; V2CipherSpec SSL_RC4_128_WITH_MD5 = { 0x01,0x00,0x80 };
V2CipherSpec SSL_RC4_128_EXPORT40_WITH_MD5 = { 0x02,0x00,0x80 }; V2CipherSpec SSL_RC4_128_EXPORT40_WITH_MD5 = { 0x02,0x00,0x80 };
V2CipherSpec SSL_RC2_CBC_128_CBC_WITH_MD5 = { 0x03,0x00,0x80 }; V2CipherSpec SSL_RC2_CBC_128_CBC_WITH_MD5 = { 0x03,0x00,0x80 };
V2CipherSpec SSL_RC2_CBC_128_CBC_EXPORT40_WITH_MD5 V2CipherSpec SSL_RC2_CBC_128_CBC_EXPORT40_WITH_MD5
= { 0x04,0x00,0x80 }; = { 0x04,0x00,0x80 };
V2CipherSpec SSL_IDEA_128_CBC_WITH_MD5 = { 0x05,0x00,0x80 }; V2CipherSpec SSL_IDEA_128_CBC_WITH_MD5 = { 0x05,0x00,0x80 };
V2CipherSpec SSL_DES_64_CBC_WITH_MD5 = { 0x06,0x00,0x40 }; V2CipherSpec SSL_DES_64_CBC_WITH_MD5 = { 0x06,0x00,0x40 };
V2CipherSpec SSL_DES_192_EDE3_CBC_WITH_MD5 = { 0x07,0x00,0xC0 }; V2CipherSpec SSL_DES_192_EDE3_CBC_WITH_MD5 = { 0x07,0x00,0xC0 };
Cipher specifications introduced in Version 3.0 can be included in Cipher specifications introduced in version 3.0 can be included in
Version 2.0 client hello messages using the syntax below. Any version 2.0 client hello messages using the syntax below. Any
V2CipherSpec element with its first byte equal to zero will be V2CipherSpec element with its first byte equal to zero will be
ignored by Version 2.0 servers. Clients sending any of the above ignored by version 2.0 servers. Clients sending any of the above
V2CipherSpecs should also include the Version 3.0 equivalent (see V2CipherSpecs should also include the version 3.0 equivalent (see
Appendix A.6): Appendix A.6):
V2CipherSpec (see Version 3.0 name) = { 0x00, CipherSuite }; V2CipherSpec (see Version 3.0 name) = { 0x00, CipherSuite };
E.1. Version 2 client hello E.1. Version 2 Client Hello
The Version 2.0 client hello message is presented below using this The version 2.0 client hello message is presented below using this
document's presentation model. The true definition is still assumed document's presentation model. The true definition is still assumed
to be the SSL Version 2.0 specification. to be the SSL version 2.0 specification.
uint8 V2CipherSpec[3]; uint8 V2CipherSpec[3];
struct { struct {
unit8 msg_type; unit8 msg_type;
Version version; Version version;
uint16 cipher_spec_length; uint16 cipher_spec_length;
uint16 session_id_length; uint16 session_id_length;
uint16 challenge_length; uint16 challenge_length;
V2CipherSpec cipher_specs[V2ClientHello.cipher_spec_length]; V2CipherSpec cipher_specs[V2ClientHello.cipher_spec_length];
opaque session_id[V2ClientHello.session_id_length]; opaque session_id[V2ClientHello.session_id_length];
Random challenge; Random challenge;
} V2ClientHello; } V2ClientHello;
session msg_type This field, in conjunction with the version field, session msg_type: This field, in conjunction with the version field,
identifies a version 2 client hello message. The value should identifies a version 2 client hello message. The value should
equal one (1). equal one (1).
version The highest version of the protocol supported by the client version: The highest version of the protocol supported by the client
(equals ProtocolVersion.version, see Appendix A.1). (equals ProtocolVersion.version; see Appendix A.1).
cipher_spec_length This field is the total length of the field cipher_spec_length: This field is the total length of the field
cipher_specs. It cannot be zero and must be a multiple of the cipher_specs. It cannot be zero and must be a multiple of the
V2CipherSpec length (3). V2CipherSpec length (3).
session_id_length This field must have a value of either zero or 16. session_id_length: This field must have a value of either zero or
If zero, the client is creating a new session. If 16, the 16. If zero, the client is creating a new session. If 16, the
session_id field will contain the 16 bytes of session session_id field will contain the 16 bytes of session
identification. identification.
challenge_length The length in bytes of the client's challenge to challenge_length: The length in bytes of the client's challenge to
the server to authenticate itself. This value must be 32. the server to authenticate itself. This value must be 32.
cipher_specs This is a list of all CipherSpecs the client is willing cipher_specs: This is a list of all CipherSpecs the client is
and able to use. There must be at least one CipherSpec acceptable willing and able to use. There must be at least one CipherSpec
to the server. acceptable to the server.
session_id If this field's length is not zero, it will contain the session_id: If this field's length is not zero, it will contain the
identification for a session that the client wishes to resume. identification for a session that the client wishes to resume.
challenge The client's challenge to the server for the server to challenge: The client's challenge to the server for the server to
identify itself is a (nearly) arbitrary length random. The identify itself is a (nearly) arbitrary length random. The
Version 3.0 server will right justify the challenge data to become version 3.0 server will right justify the challenge data to become
the ClientHello.random data (padded with leading zeroes, if the ClientHello.random data (padded with leading zeroes, if
necessary), as specified in this Version 3.0 protocol. If the necessary), as specified in this version 3.0 protocol. If the
length of the challenge is greater than 32 bytes, then only the length of the challenge is greater than 32 bytes, then only the
last 32 bytes are used. It is legitimate (but not necessary) for last 32 bytes are used. It is legitimate (but not necessary) for
a V3 server to reject a V2 ClientHello that has fewer than 16 a V3 server to reject a V2 ClientHello that has fewer than 16
bytes of challenge data. bytes of challenge data.
Note: Requests to resume an SSL 3.0 session should use an SSL 3.0 Note: Requests to resume an SSL 3.0 session should use an SSL 3.0
client hello. client hello.
E.2. Avoiding man-in-the-middle version rollback E.2. Avoiding Man-in-the-Middle Version Rollback
When SSL Version 3.0 clients fall back to Version 2.0 compatibility When SSL version 3.0 clients fall back to version 2.0 compatibility
mode, they use special PKCS #1 block formatting. This is done so mode, they use special PKCS #1 block formatting. This is done so
that Version 3.0 servers will reject Version 2.0 sessions with that version 3.0 servers will reject version 2.0 sessions with
Version 3.0-capable clients. version 3.0-capable clients.
When Version 3.0 clients are in Version 2.0 compatibility mode, they When version 3.0 clients are in version 2.0 compatibility mode, they
set the right-hand (least-significant) 8 random bytes of the PKCS set the right-hand (least-significant) 8 random bytes of the PKCS
padding (not including the terminal null of the padding) for the RSA padding (not including the terminal null of the padding) for the RSA
encryption of the ENCRYPTED-KEY- DATA field of the CLIENT-MASTER-KEY encryption of the ENCRYPTED-KEY-DATA field of the CLIENT-MASTER-KEY
to 0x03 (the other padding bytes are random). After decrypting the to 0x03 (the other padding bytes are random). After decrypting the
ENCRYPTED- KEY-DATA field, servers that support SSL 3.0 should issue ENCRYPTED-KEY-DATA field, servers that support SSL 3.0 should issue
an error if these eight padding bytes are 0x03. Version 2.0 servers an error if these eight padding bytes are 0x03. Version 2.0 servers
receiving blocks padded in this manner will proceed normally. receiving blocks padded in this manner will proceed normally.
Appendix F. Security analysis Appendix F. Security Analysis
The SSL protocol is designed to establish a secure connection between The SSL protocol is designed to establish a secure connection between
a client and a server communicating over an insecure channel. This a client and a server communicating over an insecure channel. This
document makes several traditional assumptions, including that document makes several traditional assumptions, including that
attackers have substantial computational resources and cannot obtain attackers have substantial computational resources and cannot obtain
secret information from sources outside the protocol. Attackers are secret information from sources outside the protocol. Attackers are
assumed to have the ability to capture, modify, delete, replay, and assumed to have the ability to capture, modify, delete, replay, and
otherwise tamper with messages sent over the communication channel. otherwise tamper with messages sent over the communication channel.
This appendix outlines how SSL has been designed to resist a variety This appendix outlines how SSL has been designed to resist a variety
of attacks. of attacks.
F.1. Handshake protocol F.1. Handshake Protocol
The handshake protocol is responsible for selecting a CipherSpec and The handshake protocol is responsible for selecting a CipherSpec and
generating a MasterSecret, which together comprise the primary generating a MasterSecret, which together comprise the primary
cryptographic parameters associated with a secure session. The cryptographic parameters associated with a secure session. The
handshake protocol can also optionally authenticate parties who have handshake protocol can also optionally authenticate parties who have
certificates signed by a trusted certificate authority. certificates signed by a trusted certificate authority.
F.1.1. Authentication and key exchange F.1.1. Authentication and Key Exchange
SSL supports three authentication modes: authentication of both SSL supports three authentication modes: authentication of both
parties, server authentication with an unauthenticated client, and parties, server authentication with an unauthenticated client, and
total anonymity. Whenever the server is authenticated, the channel total anonymity. Whenever the server is authenticated, the channel
should be secure against man-in- the-middle attacks, but completely should be secure against man-in-the-middle attacks, but completely
anonymous sessions are inherently vulnerable to such attacks. anonymous sessions are inherently vulnerable to such attacks.
Anonymous servers cannot authenticate clients, since the client Anonymous servers cannot authenticate clients, since the client
signature in the certificate verify message may require a server signature in the certificate verify message may require a server
certificate to bind the signature to a particular server. If the certificate to bind the signature to a particular server. If the
server is authenticated, its certificate message must provide a valid server is authenticated, its certificate message must provide a valid
certificate chain leading to an acceptable certificate authority. certificate chain leading to an acceptable certificate authority.
Similarly, authenticated clients must supply an acceptable Similarly, authenticated clients must supply an acceptable
certificate to the server. Each party is responsible for verifying certificate to the server. Each party is responsible for verifying
that the other's certificate is valid and has not expired or been that the other's certificate is valid and has not expired or been
revoked. revoked.
The general goal of the key exchange process is to create a The general goal of the key exchange process is to create a
pre_master_secret known to the communicating parties and not to pre_master_secret known to the communicating parties and not to
attackers. The pre_master_secret will be used to generate the attackers. The pre_master_secret will be used to generate the
master_secret (see Section 6.1). The master_secret is required to master_secret (see Section 6.1). The master_secret is required to
generate the finished messages, encryption keys, and MAC secrets (see generate the finished messages, encryption keys, and MAC secrets (see
Section 5.6.9 and Section 6.2.2). By sending a correct finished Sections 5.6.9 and 6.2.2). By sending a correct finished message,
message, parties thus prove that they know the correct parties thus prove that they know the correct pre_master_secret.
pre_master_secret.
F.1.1.1. Anonymous key exchange F.1.1.1. Anonymous Key Exchange
Completely anonymous sessions can be established using RSA, Diffie- Completely anonymous sessions can be established using RSA, Diffie-
Hellman, or FORTEZZA for key exchange. With anonymous RSA, the Hellman, or FORTEZZA for key exchange. With anonymous RSA, the
client encrypts a pre_master_secret with the server's uncertified client encrypts a pre_master_secret with the server's uncertified
public key extracted from the server key exchange message. The public key extracted from the server key exchange message. The
result is sent in a client key exchange message. Since eavesdroppers result is sent in a client key exchange message. Since eavesdroppers
do not know the server's private key, it will be infeasible for them do not know the server's private key, it will be infeasible for them
to decode the pre_master_secret. to decode the pre_master_secret.
With Diffie-Hellman or FORTEZZA, the server's public parameters are With Diffie-Hellman or FORTEZZA, the server's public parameters are
contained in the server key exchange message and the client's are contained in the server key exchange message and the client's are
sent in the client key exchange message. Eavesdroppers who do not sent in the client key exchange message. Eavesdroppers who do not
know the private values should not be able to find the Diffie-Hellman know the private values should not be able to find the Diffie-Hellman
result (i.e. the pre_master_secret) or the FORTEZZA token encryption result (i.e., the pre_master_secret) or the FORTEZZA token encryption
key (TEK). key (TEK).
Warning: Completely anonymous connections only provide protection Warning: Completely anonymous connections only provide protection
against passive eavesdropping. Unless an independent tamper-proof against passive eavesdropping. Unless an independent tamper-proof
channel is used to verify that the finished messages were not channel is used to verify that the finished messages were not
replaced by an attacker, server authentication is required in replaced by an attacker, server authentication is required in
environments where active man-in-the-middle attacks are a concern. environments where active man-in-the-middle attacks are a concern.
F.1.1.2. RSA key exchange and authentication F.1.1.2. RSA Key Exchange and Authentication
With RSA, key exchange and server authentication are combined. The With RSA, key exchange and server authentication are combined. The
public key may be either contained in the server's certificate or may public key either may be contained in the server's certificate or may
be a temporary RSA key sent in a server key exchange message. When be a temporary RSA key sent in a server key exchange message. When
temporary RSA keys are used, they are signed by the server's RSA or temporary RSA keys are used, they are signed by the server's RSA or
DSS certificate. The signature includes the current DSS certificate. The signature includes the current
ClientHello.random, so old signatures and temporary keys cannot be ClientHello.random, so old signatures and temporary keys cannot be
replayed. Servers may use a single temporary RSA key for multiple replayed. Servers may use a single temporary RSA key for multiple
negotiation sessions. negotiation sessions.
Note: The temporary RSA key option is useful if servers need large Note: The temporary RSA key option is useful if servers need large
certificates but must comply with government-imposed size limits on certificates but must comply with government-imposed size limits on
keys used for key exchange. keys used for key exchange.
skipping to change at page 63, line 26 skipping to change at page 63, line 25
message, the server demonstrates that it knows the private key message, the server demonstrates that it knows the private key
corresponding to the server certificate. corresponding to the server certificate.
When RSA is used for key exchange, clients are authenticated using When RSA is used for key exchange, clients are authenticated using
the certificate verify message (see Section 5.6.8). The client signs the certificate verify message (see Section 5.6.8). The client signs
a value derived from the master_secret and all preceding handshake a value derived from the master_secret and all preceding handshake
messages. These handshake messages include the server certificate, messages. These handshake messages include the server certificate,
which binds the signature to the server, and ServerHello.random, which binds the signature to the server, and ServerHello.random,
which binds the signature to the current handshake process. which binds the signature to the current handshake process.
F.1.1.3. Diffie-Hellman key exchange with authentication F.1.1.3. Diffie-Hellman Key Exchange with Authentication
When Diffie-Hellman key exchange is used, the server can either When Diffie-Hellman key exchange is used, the server either can
supply a certificate containing fixed Diffie-Hellman parameters or supply a certificate containing fixed Diffie-Hellman parameters or
can use the server key exchange message to send a set of temporary can use the server key exchange message to send a set of temporary
Diffie-Hellman parameters signed with a DSS or RSA certificate. Diffie-Hellman parameters signed with a DSS or RSA certificate.
Temporary parameters are hashed with the hello.random values before Temporary parameters are hashed with the hello.random values before
signing to ensure that attackers do not replay old parameters. In signing to ensure that attackers do not replay old parameters. In
either case, the client can verify the certificate or signature to either case, the client can verify the certificate or signature to
ensure that the parameters belong to the server. ensure that the parameters belong to the server.
If the client has a certificate containing fixed Diffie- Hellman If the client has a certificate containing fixed Diffie-Hellman
parameters, its certificate contains the information required to parameters, its certificate contains the information required to
complete the key exchange. Note that in this case the client and complete the key exchange. Note that in this case, the client and
server will generate the same Diffie- Hellman result (i.e., server will generate the same Diffie-Hellman result (i.e.,
pre_master_secret) every time they communicate. To prevent the pre_master_secret) every time they communicate. To prevent the
pre_master_secret from staying in memory any longer than necessary, pre_master_secret from staying in memory any longer than necessary,
it should be converted into the master_secret as soon as possible. it should be converted into the master_secret as soon as possible.
Client Diffie- Hellman parameters must be compatible with those Client Diffie-Hellman parameters must be compatible with those
supplied by the server for the key exchange to work. supplied by the server for the key exchange to work.
If the client has a standard DSS or RSA certificate or is If the client has a standard DSS or RSA certificate or is
unauthenticated, it sends a set of temporary parameters to the server unauthenticated, it sends a set of temporary parameters to the server
in the client key exchange message, then optionally uses a in the client key exchange message, then optionally uses a
certificate verify message to authenticate itself. certificate verify message to authenticate itself.
F.1.1.4. FORTEZZA F.1.1.4. FORTEZZA
FORTEZZA's design is classified, but at the protocol level it is FORTEZZA's design is classified, but at the protocol level it is
similar to Diffie-Hellman with fixed public values contained in similar to Diffie-Hellman with fixed public values contained in
certificates. The result of the key exchange process is the token certificates. The result of the key exchange process is the token
encryption key (TEK), which is used to wrap data encryption keys, encryption key (TEK), which is used to wrap data encryption keys,
client write key, server write key, and master secret encryption key. client write key, server write key, and master secret encryption key.
The data encryption keys are not derived from the pre_master_secret The data encryption keys are not derived from the pre_master_secret
because unwrapped keys are not accessible outside the token. The because unwrapped keys are not accessible outside the token. The
encrypted pre_master_secret is sent to the server in a client key encrypted pre_master_secret is sent to the server in a client key
exchange message. exchange message.
F.1.2. Version rollback attacks F.1.2. Version Rollback Attacks
Because SSL Version 3.0 includes substantial improvements over SSL Because SSL version 3.0 includes substantial improvements over SSL
Version 2.0, attackers may try to make Version 3.0- capable clients version 2.0, attackers may try to make version 3.0-capable clients
and servers fall back to Version 2.0. This attack is occurring if and servers fall back to version 2.0. This attack is occurring if
(and only if) two Version 3.0-capable parties use an SSL 2.0 (and only if) two version 3.0-capable parties use an SSL 2.0
handshake. handshake.
Although the solution using non-random PKCS #1 block type 2 message Although the solution using non-random PKCS #1 block type 2 message
padding is inelegant, it provides a reasonably secure way for Version padding is inelegant, it provides a reasonably secure way for version
3.0 servers to detect the attack. This solution is not secure 3.0 servers to detect the attack. This solution is not secure
against attackers who can brute force the key and substitute a new against attackers who can brute force the key and substitute a new
ENCRYPTED-KEY-DATA message containing the same key (but with normal ENCRYPTED-KEY-DATA message containing the same key (but with normal
padding) before the application specified wait threshold has expired. padding) before the application specified wait threshold has expired.
Parties concerned about attacks of this scale should not be using 40- Parties concerned about attacks of this scale should not be using 40-
bit encryption keys anyway. Altering the padding of the least- bit encryption keys anyway. Altering the padding of the least
significant 8 bytes of the PKCS padding does not impact security, significant 8 bytes of the PKCS padding does not impact security,
since this is essentially equivalent to increasing the input block since this is essentially equivalent to increasing the input block
size by 8 bytes. size by 8 bytes.
F.1.3. Detecting attacks against the handshake protocol F.1.3. Detecting Attacks against the Handshake Protocol
An attacker might try to influence the handshake exchange to make the An attacker might try to influence the handshake exchange to make the
parties select different encryption algorithms than they would parties select different encryption algorithms than they would
normally choose. Because many implementations will support 40-bit normally choose. Because many implementations will support 40-bit
exportable encryption and some may even support null encryption or exportable encryption and some may even support null encryption or
MAC algorithms, this attack is of particular concern. MAC algorithms, this attack is of particular concern.
For this attack, an attacker must actively change one or more For this attack, an attacker must actively change one or more
handshake messages. If this occurs, the client and server will handshake messages. If this occurs, the client and server will
compute different values for the handshake message hashes. As a compute different values for the handshake message hashes. As a
result, the parties will not accept each others' finished messages. result, the parties will not accept each other's finished messages.
Without the master_secret, the attacker cannot repair the finished Without the master_secret, the attacker cannot repair the finished
messages, so the attack will be discovered. messages, so the attack will be discovered.
F.1.4. Resuming sessions F.1.4. Resuming Sessions
When a connection is established by resuming a session, new When a connection is established by resuming a session, new
ClientHello.random and ServerHello.random values are hashed with the ClientHello.random and ServerHello.random values are hashed with the
session's master_secret. Provided that the master_secret has not session's master_secret. Provided that the master_secret has not
been compromised and that the secure hash operations used to produce been compromised and that the secure hash operations used to produce
the encryption keys and MAC secrets are secure, the connection should the encryption keys and MAC secrets are secure, the connection should
be secure and effectively independent from previous connections. be secure and effectively independent from previous connections.
Attackers cannot use known encryption keys or MAC secrets to Attackers cannot use known encryption keys or MAC secrets to
compromise the master_secret without breaking the secure hash compromise the master_secret without breaking the secure hash
operations (which use both SHA and MD5). operations (which use both SHA and MD5).
skipping to change at page 65, line 30 skipping to change at page 65, line 30
force a full handshake. An upper limit of 24 hours is suggested for force a full handshake. An upper limit of 24 hours is suggested for
session ID lifetimes, since an attacker who obtains a master_secret session ID lifetimes, since an attacker who obtains a master_secret
may be able to impersonate the compromised party until the may be able to impersonate the compromised party until the
corresponding session ID is retired. Applications that may be run in corresponding session ID is retired. Applications that may be run in
relatively insecure environments should not write session IDs to relatively insecure environments should not write session IDs to
stable storage. stable storage.
F.1.5. MD5 and SHA F.1.5. MD5 and SHA
SSL uses hash functions very conservatively. Where possible, both SSL uses hash functions very conservatively. Where possible, both
MD5 and SHA are used in tandem to ensure that non- catastrophic flaws MD5 and SHA are used in tandem to ensure that non-catastrophic flaws
in one algorithm will not break the overall protocol. in one algorithm will not break the overall protocol.
F.2. Protecting application data F.2. Protecting Application Data
The master_secret is hashed with the ClientHello.random and The master_secret is hashed with the ClientHello.random and
ServerHello.random to produce unique data encryption keys and MAC ServerHello.random to produce unique data encryption keys and MAC
secrets for each connection. FORTEZZA encryption keys are generated secrets for each connection. FORTEZZA encryption keys are generated
by the token, and are not derived from the master_secret. by the token, and are not derived from the master_secret.
Outgoing data is protected with a MAC before transmission. To Outgoing data is protected with a MAC before transmission. To
prevent message replay or modification attacks, the MAC is computed prevent message replay or modification attacks, the MAC is computed
from the MAC secret, the sequence number, the message length, the from the MAC secret, the sequence number, the message length, the
message contents, and two fixed character strings. The message type message contents, and two fixed-character strings. The message type
field is necessary to ensure that messages intended for one SSL field is necessary to ensure that messages intended for one SSL
Record Layer client are not redirected to another. The sequence record layer client are not redirected to another. The sequence
number ensures that attempts to delete or reorder messages will be number ensures that attempts to delete or reorder messages will be
detected. Since sequence numbers are 64-bits long, they should never detected. Since sequence numbers are 64 bits long, they should never
overflow. Messages from one party cannot be inserted into the overflow. Messages from one party cannot be inserted into the
other's output, since they use independent MAC secrets. Similarly, other's output, since they use independent MAC secrets. Similarly,
the server-write and client-write keys are independent so stream the server-write and client-write keys are independent so stream
cipher keys are used only once. cipher keys are used only once.
If an attacker does break an encryption key, all messages encrypted If an attacker does break an encryption key, all messages encrypted
with it can be read. Similarly, compromise of a MAC key can make with it can be read. Similarly, compromise of a MAC key can make
message modification attacks possible. Because MACs are also message modification attacks possible. Because MACs are also
encrypted, message-alteration attacks generally require breaking the encrypted, message-alteration attacks generally require breaking the
encryption algorithm as well as the MAC. encryption algorithm as well as the MAC.
Note: MAC secrets may be larger than encryption keys, so messages can Note: MAC secrets may be larger than encryption keys, so messages can
remain tamper resistant even if encryption keys are broken. remain tamper resistant even if encryption keys are broken.
F.3. Final notes F.3. Final Notes
For SSL to be able to provide a secure connection, both the client For SSL to be able to provide a secure connection, both the client
and server systems, keys, and applications must be secure. In and server systems, keys, and applications must be secure. In
addition, the implementation must be free of security errors. addition, the implementation must be free of security errors.
The system is only as strong as the weakest key exchange and The system is only as strong as the weakest key exchange and
authentication algorithm supported, and only trustworthy authentication algorithm supported, and only trustworthy
cryptographic functions should be used. Short public keys, 40-bit cryptographic functions should be used. Short public keys, 40-bit
bulk encryption keys, and anonymous servers should be used with great bulk encryption keys, and anonymous servers should be used with great
caution. Implementations and users must be careful when deciding caution. Implementations and users must be careful when deciding
which certificates and certificate authorities are acceptable; a which certificates and certificate authorities are acceptable; a
dishonest certificate authority can do tremendous damage. dishonest certificate authority can do tremendous damage.
Appendix G. Acknowledgements Appendix G. Acknowledgements
G.1. Other contributors G.1. Other Contributors
Martin Abadi Robert Relyea Martin Abadi Robert Relyea
Digital Equipment Corporation Netscape Communications Digital Equipment Corporation Netscape Communications
ma@pa.dec.com relyea@netscape.com ma@pa.dec.com relyea@netscape.com
Taher Elgamal Jim Roskind Taher Elgamal Jim Roskind
Netscape Communications Netscape Communications Netscape Communications Netscape Communications
elgamal@netscape.com jar@netscape.com elgamal@netscape.com jar@netscape.com
Anil Gangolli Micheal J. Sabin, Ph. D. Anil Gangolli Micheal J. Sabin, Ph.D.
Netscape Communications Consulting Engineer Netscape Communications Consulting Engineer
gangolli@netscape.com msabin@netcom.com gangolli@netscape.com msabin@netcom.com
Kipp E.B. Hickman Tom Weinstein Kipp E.B. Hickman Tom Weinstein
Netscape Communications Netscape Communications Netscape Communications Netscape Communications
kipp@netscape.com tomw@netscape.com kipp@netscape.com tomw@netscape.com
G.2. Early reviewers G.2. Early Reviewers
Robert Baldwin Clyde Monma Robert Baldwin Clyde Monma
RSA Data Security, Inc. Bellcore RSA Data Security, Inc. Bellcore
baldwin@rsa.com clyde@bellcore.com baldwin@rsa.com clyde@bellcore.com
George Cox Eric Murray George Cox Eric Murray
Intel Corporation ericm@lne.com Intel Corporation ericm@lne.com
cox@ibeam.jf.intel.com cox@ibeam.jf.intel.com
Cheri Dowell Avi Rubin Cheri Dowell Avi Rubin
Sun Microsystems Bellcore Sun Microsystems Bellcore
cheri@eng.sun.com rubin@bellcore.com cheri@eng.sun.com rubin@bellcore.com
Stuart Haber Don Stephenson Stuart Haber Don Stephenson
Bellcore Sun Microsystems Bellcore Sun Microsystems
stuart@bellcore.com don.stephenson@eng.sun.com stuart@bellcore.com don.stephenson@eng.sun.com
Burt Kaliski Joe Tardo Burt Kaliski Joe Tardo
RSA Data Security, Inc. General Magic RSA Data Security, Inc. General Magic
burt@rsa.com tardo@genmagic.com burt@rsa.com tardo@genmagic.com
Authors' Addresses Authors' Addresses
Alan O. Freier Alan O. Freier
Netscape communications Netscape Communications
Philip Karlton Philip Karlton
Netscape communications Netscape Communications
Paul C. Kocher Paul C. Kocher
Independent consultant Independent Consultant
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