ccrypt is a utility for encrypting and decrypting files and streams.
It was designed as a replacement for the standard unix crypt utility,
which is notorious for using a very weak encryption algorithm.

ccrypt is based on the Rijndael cipher, which is the U.S. government's
chosen candidate for the Advanced Encryption Standard (AES, see
http://www.nist.gov/aes). This cipher is believed to provide very strong
security.