crypt

crypt [password] < file > encryptedfile

Encrypt a file to prevent unauthorized access. password is either a string of characters you choose or the option -k, which assigns the value of the environment variable CRYPTKEY (Solaris: CrYpTkEy) as the password. The same password encrypts a file or decrypts an encrypted file. If no password is given, crypt prompts for one. crypt is available only in the United States (due to export restrictions).

The algorithm used is considered weak, and this command should not be used for serious encryption. See PGP: Pretty Good Privacy, listed in the Bibliography.