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

US6243470A · kind A · utility

Assignee

• International Business Machines Corporation · US

Inventors

• Don Coppersmith · Ossining, US
• Rosario Gennaro · The Bronx, US
• Shai Halevi · Elmsford, US
• Charanjit Singh Jutla · New York, US
• Stephen M. Matyas · Manassas, US
• Mohammed Peyravian · Cary, US
• David R. Safford · Brewster, US
• Nevenko Zunic · Wappingers Falls, US

Key dates

• Filing date: Feb 4, 1998
• Grant date: Jun 5, 2001
• Expiry date: Feb 4, 2018

Classification

• Technology area (CPC H): Electricity
• CPC primary: H04L2209/24
• WIPO field: Digital communication
• WIPO sector: Electrical engineering

Abstract

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.