| Cypherspace Find information on some cryptanalytic hacks, breaking weak cryptosystems and links to more cryptography related websites. - read more | |
| The Cipher Challenge History of a code cracking competition. Challenge details, how it was solved, winners, essays and photo gallery. - read more | |
| Crypto Machines Features machines and systems used in secure communications. Includes brief history on cryptography. - read more | |
| International Cryptography Freedom Links to cryptography related downloads and information from around the world. - read more | |
