CAST-256

CAST -256 is a block cipher published in 1998. It represents an extension and improvement of the block cipher CAST -128 dar. Both are based on the design methods of " CAST " which were developed by Carlisle Adams and Stafford Tavares. CAST -256 is specified in RFC 2612.

CAST -256 was in the selection process for the Advanced Encryption Standard (AES ) and assigns against the winner Rijndael implementations both in hardware and in software a lower data throughput. CAST -256 itself was not among the finalists.

CAST CAST -128 256 is as a Feistelchiffre and uses the same round function in which, inter alia, four S-boxes are used. But it has a different block size of four words of 32 bits and a number of laps 48. In each round, a word is calculated from a data word and key bit 37 which is XORed with another data word. Valid key lengths are 128, 160, 192, 224 or 256 bits. According to RFC 2612 CAST -256 can be used cost and royalty free in all commercial and non -commercial applications worldwide.