CAST-256

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In cryptography, CAST-256 (or CAST6) is a block cipher published in June 1998 and submitted as a candidate for the Advanced Encryption Standard (AES). It is an extension of an earlier cipher, CAST-128; both were designed according to the "CAST" design methodology invented by Carlisle Adams and Stafford Tavares. Howard Heys and Michael Wiener also contributed to the design.

CAST-256 uses the same elements as CAST-128, including S-boxes, but is adapted for a block size of 128 bits — twice the size of its 64-bit predecessor. (A similar construction occurred in the evolution of RC5 into RC6). Acceptable key sizes are 128, 160, 192, 224 or 256 bits. CAST-256 is composed of 48 rounds, sometimes described as 12 "quad-rounds", arranged in a generalised Feistel network.

In RFC 2612, the authors state that, "The CAST-256 cipher described in this document is available worldwide on a royalty-free and licence-free basis for commercial and non-commercial uses."

[edit] See also

• AES process

[edit] External links

• John Savard's description of CAST-256 Archive
• SCAN's entry for CAST-256
• RFC 2612
• Discussion of CAST-256 algorithm and source samples

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