How do you keep a secret? One way is esczfrs ncjaezrclasj.* If you understood that, you already may know a little about cryptography.

For more than 3,000 years, people have encrypted messages to keep their communications secret. And encryption is still used today, though it’s much more sophisticated from the simple encryption from our past.

To make a successful cipher, you need a few things: an algorithm and a key to encrypt the information and an identical key and algorithm to decrypt the information. The key is known only by the message’s originator and recipient, and must be kept secret.

Simple Ciphers

You may be familiar with some of the most basic ciphers, which many of us used with the secret decoder rings from our childhood. We used that same cipher – a substitution cipher – at the top of our story. There are various substitution ciphers, but one of the easiest is the Caesar cipher, also known as the shift cipher.

This cipher is named after Julius Caesar, who is said to have used this simple cipher to communicate with his army. To secure his messages, Caesar shifted the letters of the alphabet and sent messages that looked like scrambled text to those who did not hold the key. The recipients of his message knew the letter shift algorithm and could easily decipher the message – once they knew how many letters to shift for the key.

But these simple ciphers, though fun to use, are not secure. In the world of intelligence, banking, computer science, among others, more advanced encryption is needed to secure secrets. We deal with these advanced encryptions in our everyday lives, as well – every time we use our ATM card or type in our computer password.

Complex Ciphers

During World War II, the Germans used Enigma, a cipher machine, to develop nearly unbreakable codes for sending messages. Enigma’s settings offered 150,000,000,000,000,000,000 possible solutions, yet the Allies were eventually able to crack its code.

The machine was developed by the Dutch to communicate banking secrets. The Germans bought the patent in 1923 for intelligence purposes. Polish intelligence was able to purchase an Enigma at a trade fair and procure a codebook from a French agent. When Poland was overrun in 1939, they realized they wouldn’t have capabilities to solve code. The Poles gave the information and machine to the allies.

By end of the war, we were reading 10 percent of all German Enigma communications at Bletchley Park, in England, on the world’s first electromagnetic computers. (Learn more about Enigma and other mechanisms used to communicate secret information (like the one-time pad) in the CIA Museum virtual tour.)

Enigma was just the beginning of how complex cryptography has become. In today’s world – where people maintain and transmit secret data digitally – ciphers have become increasingly complex.

One of the most secure codes is in a piece of artwork at CIA’s Headquarters. Kryptos has been on display at Agency headquarters for nearly 20 years. In that time, no one has ever fully deciphered Kryptos’ coded message. Try your skills at decoding Kryptos at https://www.cia.gov/about-cia/virtual-tour/kryptos/index.html.

If you want to start on some easier codes, visit the “Break the Code” section on our Kids’ Page: https://www.cia.gov/kids-page/games/break-the-code/index.html.

*esczfrs ncjaezrclasj translates to “through cryptography” using the Caesar cipher. With this simple cipher, we shifted the alphabet by 11 places, so A equals L, B equals M, etc.