International Business Machines Corporation

Mohammed Peyravian

Nevenko Zunic

David R Safford

Shai Halevi

Stephen Michael Matyas, Jr

Charanjit Singh Jutla

Don Coppersmith

Rosario Gennaro

Luke James O'Connor

A method and apparatus for an advanced symmetric key cipher for encryption and decryption, using a block cipher algorithm. Different block sizes and key sizes are supported, and a different sub-key is used in each round. Encryption is computed using a variable number of rounds of mixing, permutation, and key-dependent substitution. Decryption uses a variable number of rounds of key-dependent inverse substitution, inverse permutation and inverse mixing. The variable length sub-keys are data-independent, and can be precomputed.

Method and apparatus for advanced symmetric key block cipher with variable length key and block

A method and apparatus for an advanced byte-oriented symmetric key cipher for encryption and decryption, using a block cipher algorithm. Different block sizes and key sizes are supported, and a different sub-key is used in each round. Encryption is computed using a variable number of rounds of mixing, permutation, and key-dependent substitution. Decryption uses a variable number of rounds of key-dependent inverse substitution, inverse permutation, and inverse mixing. The variable length sub-keys are data-independent, and can be precomputed.

Method and apparatus for advanced byte-oriented symmetric key block cipher with variable length key and block

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).

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

The present invention provides a technique, system, and computer program for a symmetric key block cipher. Variable block sizes and key sizes are supported, as well as a variable number of rounds. The cipher uses multiple stages of processing, where the stages have different structures and different subround functions, to provide excellent resistance to both linear and differential attacks. Feistel Type-3 networks are used, with different networks during different stages. The number of rounds may vary among stages. Subkeys are used in some, but not all, stages. The variable-length keys can be precomputed. A novel manner of using multiplication in a cipher is defined.

Method and apparatus for a symmetric block cipher using multiple stages

The present invention provides a technique, system, and computer program for a symmetric key block cipher. Variable block sizes and key sizes are supported, as well as a variable number of rounds. The cipher uses multiple stages of processing, where the stages have different structures and different subround functions, to provide excellent resistance to both linear and differential attacks. Feistel Type-1 and Type-3 are both used, each during different stages. The number of rounds may vary among stages. Subkeys are used in some, but not all, stages. The variable-length keys can be precomputed. A novel manner of using data-dependent rotation in a cipher is defined.

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Cary, NC, United States of America

Mohammed Peyravian