mcrypt is a replacement for the popular Unix crypt command.
crypt was a file encryption tool that used an algorithm very close to the World War II Enigma cipher.
Libmcrypt, Mcrypt's companion, is a library of code that contains the actual encryption functions and provides an easy method for use.
[3] Examples of mcrypt usage in a Linux command-line environment: It implements numerous cryptographic algorithms, mostly block ciphers and stream ciphers, some of which fall under export restrictions in the United States.
Algorithms include DES, Blowfish, ARCFOUR, Enigma, GOST, LOKI97, RC2, Serpent, Threeway, Twofish, WAKE, and XTEA.