CAST-256

Infobox block cipher
name = CAST-256


caption =
designers = Carlisle Adams, Stafford Tavares, Howard Heys, Michael Wiener
publish date = 1998
derived from = CAST-128
derived to =
key size = 128, 192 or 256 bits
block size = 128 bits
structure = generalised Feistel network
rounds = 48
cryptanalysis =In cryptography, CAST-256 (or CAST6) is a block cipher published in June 1998. It was submitted as a candidate for the Advanced Encryption Standard (AES); however, it was not among the five AES finalists. 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."

ee also

* AES process

External links

* [http://www.quadibloc.com/crypto/co040410.htm John Savard's description of CAST-256] Archive
* [http://www.users.zetnet.co.uk/hopwood/crypto/scan/cs.html#CAST-256 SCAN's entry for CAST-256]
* [http://www.rfc-editor.org/rfc/rfc2612.txt RFC 2612]