- Codes and Ciphers in the Second World War
 - Provides a look at the history, science, and engineering of cryptanalysis in World War II. - Famous Unsolved Codes and Ciphers
- Unofficial list of well-known unsolved codes and ciphers, from the Beale Ciphers to the Richard Feynman Challenge. Also include untranslated ancient scripts like Linear A.
- Secret Language
- Step-by-step overview of ciphers and substitution codes for the amateur secret agent. Learn about cipher wheels and diagrams, transpositions, and frequencies.
- Codes, Ciphers,and Codebreaking
- A general introduction to the ciphers and codes used to protect secret data. Covers basic concepts, cryptology and cryptanalysis, codebreakers in history, and mechanized ciphers.
- Codes and Ciphers
- Essay about the use of ciphers and codes to disguise secret messages throughout history. Learn about the Caesar Substitution Cipher, polyalphabetic substitution, and World War II's Enigma machine.
- Historical Ciphers
- Profiles of famous codes and ciphers in history. Learn about the simple subsitution cipher, the Vigenere Cipher, the Enigma Machine, and PGP encryption.
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