CAST-256 (or CAST6 ) is a Encryption algorithm per block derived from CAST-128 (published in 1996). CAST-256 was published in June 1998 and was candidate for AES. It uses the same elements as CAST-128 with however S-Box are adapted to a size of block of 128 bits. The keys have a size which varies between 128 and 256 bits (by increment of 32 bits). The algorithm uses 48 rounds, sometimes referred under the term of 12 “quad-rounds”, laid out according to a Réseau of Feistel balanced. During the selection for AES, it was close to Serpent of Eli Biham but was not retained for the second round. Its conservatism in term of safety was done with the detriment of the performance and prevented it from going further in the contest.

CAST-256 is available and usable free according to a license which authorizes the commercial or not-commercial use.

References

• C.M. Adams. (1997). " Constructing Symmetric Ciphers Using the CAST Procedure" Design; , Designs, Codes, and Cryptography , 12 (3), pp. 283-316.
• C.M. Adams, " CAST Design Addendum" Procedure;.
• Bruce Schneier, 1996, Applied Cryptography, 2nd edition. John Wiley & Sounds. pp334-335. ISBN 0-471-11709-9

External bonds

• algorithm CAST-256 (RFC)