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Patent Title: Symmetric block cipher using multiple stages with modified type-1 and type-3 feistel networks

Assignee: IBM
Patent Number: US6189095
Issue Date: 02-13-2001
Application Number:
File Date:06-05-1998

Abstract: The present invention provides a technique, system, and computer program for a symmetric key block cipher. This cipher uses multiple stages with a modified Type-3 Feistel network, and a modified Unbalanced Type-1 Feistel network in an expansion box forward function. The cipher allows the block size, key size, number of rounds of expansion, and number of stages of ciphering to vary. The modified Type-3 cipher modifies the word used as input to the expansion box in certain rounds, to speed the diffusion properties of the ciphering. The modified Type-3 and Type-1 ciphers are interleaved, and provide excellent resistance to both linear and differential attacks. The variable-length subkeys and the S-box can be precomputed. A minimal amount of computer storage is required to implement this cipher, which can be implemented equally well in hardware or software (or some combination thereof).

Notes:

Link to USPTO

IBM Pledge dated 1/11/2005