Methods and apparatus for enhanced security expansion of a secret key into a lookup table for improved security for wireless telephone messages

US6233337A · kind A · utility

Assignee

• LUCENT TECHNOLOGIES INC. · US

Inventors

• Mark H. Etzel · Harvard, US
• Robert John Frank · Silver Spring, US
• Daniel Nelson Heer · Berlin, DE
• Robert Joseph McNelis · Columbia, US
• Semyon B. Mizikovsky · Morganville, US
• Robert J. Rance · Bradford, US
• R. Dale Shipp · Columbia, US

Key dates

• Filing date: Apr 13, 1998
• Grant date: May 15, 2001
• Expiry date: Apr 13, 2018

Classification

• Technology area (CPC H): Electricity
• CPC primary: H04L2209/80
• WIPO field: Digital communication
• WIPO sector: Electrical engineering

Abstract

An enhancement to the use of a tbox function for CMEA encryption. Offsets are generated for application of the tbox function to a message, using secret values and previously encrypted message octets. The offsets are used to permute the message for application of the tbox function. For the first message of a call, the previously encrypted message octets are replaced by an initialization value. In a system employing a single iteration of CMEA encryption, first and second offsets are generated. In a system employing two iterations of CMEA encryption, first, second, third and fourth offsets are generated, with the first and second offsets being used in the first iteration of CMEA encryption and the third and fourth offsets being used in the second iteration of CMEA encryption.