secure encryption and decryption of files and streams

 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.