Random Number Generation

Generally-speaking, there are two types of random number generators (RNGs):

1. RNGs based on Deterministic Random Bit Generators (DRBGs), also known as Pseudorandom Number Generators, and
2. RNGs based on Non-deterministic Random Bit Generators (NRBGs), also known as "True" Random Number Generators.

Approved Algorithms

Currently, there exists several Approved DRBGs, and no Approved NRBGs.

Deterministic Generators

FIPS 186-2, Digital Signature Standard (DSS), defines two deterministic techniques for generating numbers. See Appendices 3.1 and 3.2 and Change Notice #1 of FIPS 186-2.

ANSI X9.31 Appendix A.2.4 specifies a technique for generating pseudorandom numbers. This is the same technique (using DES) that was specified in Appendix C of ANSI X9.17.

ANSI X9.62-1998 Annex A.4 specifies an additional algorithm derived from FIPS 186.

NIST Special Publication (SP) 800-90, Recommendation for Random Number Generation Using Deterministic Random Bit Generators (Revised) , specifies four DRBGs and briefly discusses entropy sources and methods for creating an RNG from an entropy source and an Approved DRBG.

Non-Deterministic Generators

There are no Approved NRBGs.

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Testing Products

Testing requirements and validation lists are available from the Cryptographic Algorithm Validation Program (CAVP).

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RNG Testing

NIST Special Publication 800-22, A Statistical Test Suite for Random and Pseudorandom Number Generators, May 2001 (rev.).

SP 800-22 provides a set of statistical tests for testing and evaluating deterministic and non-deterministic random number generators.

NIST has published an ITL Bulletin that summarizes SP 800-22.

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Additional Information

NIST maintains a general web page on Random Number Generation and Testing that contains links to documentation and code.

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RNG Workshop and Standards Development

A workshop on random number generation was held from July 19-22, 2004 at NIST. The following information is available for interested parties:

1. Agenda
2. RNG Development History
3. RNG Standard Strategy
4. X9.82, Part 1
5. X9.82, Part 3
6. Hash and Block Cipher-based DRBGs
7. Number Theoretic DRBGs,
8. X9.82, Part 2 (forthcoming)
9. Entropy Sources
10. Testing Issues with OS-based Entropy Sources
11. Validation Testing and NIST Statistical Test Suite
12. Block Cipher-based DRBGs

The permission to post the draft of X9.82 has expired; therefore, it is no longer available on this website. Comments received can be viewed here. Additional comments on the ANSI X9.82 and comments in general may be sent to ebarker@nist.gov or John.Kelsey@nist.gov.