Skipjack

SKIPJACK is a classified, symmetric key, encryption algorithm developed by the National Security Agency to provide secure voice and data communications while allowing lawful access to those communications by law enforcement. SKIPJACK transforms a 64-bit input block into a 64-bit output block, and can be used in the same four modes of operation specified for the DES. The secret key length for SKIPJACK is 80 bits, however, as opposed to 56 bits for the DES, thereby allowing over 16,000,000 times more keys than the DES. SKIPJACK also scrambles the data in 32 rounds per single encrypt/decrypt operation, compared with 16 rounds for the DES.