Paper 2004/301

VMPC-MAC: A Stream Cipher Based Authenticated Encryption Scheme

Bartosz Zoltak

Abstract

A stream cipher based algorithm for computing Message Authentication Codes is described. The algorithm employs the internal state of the underlying cipher to minimize the required additional-to-encryption computational effort and maintain general simplicity of the design. The scheme appears to provide proper statistical properties, a comfortable level of resistance against forgery attacks in a chosen ciphertext attack model and high efficiency in software implementations.

Note: VMPC-MAC is a successor to the Tail-MAC scheme, which was broken with complexity 2^32. Tail-MAC's description with an outline of two strong attacks can be found at ePrint as report 2004/048. The VMPC-MAC scheme solves all the security problems found in the Tail-MAC and employs a different approach - it is a cipher-specific, dedicated to the VMPC Stream Cipher, rather than a general scheme.