SAFER (cipher)

SAFER, for Secure and Fast Encryption Routine, is the name for a series of block ciphers designed by James Massey and co-workers for Cylink Corporation. All of these ciphers are unpatented and freely available for any use. There have been published attacks on some of them, but later versions have modifications to block those attacks.

The first series of SAFER ciphers all had 64-bit block size. They had names like SAFER K-64 and SAFER K-128, with the number indicating key size. Lars Knudsen and others found some weaknesses in the key schedule and those were fixed, giving SAFER SK-64 and SAFER SK-128, The "SK" stands for "Strengthened Key schedule", but the RSA FAQ claimst, "one joke has it that SK really stands for 'Stop Knudsen', a wise precaution in the design of any block cipher".

Safer+ was candidate in the AES competition; it did not make it into the finals. Like all AES candidates, it uses 128-bit blocks and supports key sizes of 128, 192 or 256 bits. It is an SP network using two S-boxes. 8 rounds are used with a 128-bit key, 12 for a 192-bit key, and 15 for a 256-bit key.