Paper 2007/124

Rebuttal of overtaking VEST

Benjamin Gittins and Howard Landman

Abstract

VEST is a set of four stream cipher families targeted to semiconductor applications. All VEST family members support efficient encryption, single pass authenticated encryption, and collision resistant hashing in the one low area module. VEST was submitted by Synaptic Laboratories to the ECRYPT NoE eSTREAM project in 2005. Recently, a single digit typographical error was identified in the VEST counter diffuser description. Shortly afterwards Antoine Joux and Jean-René Reinhard published collisions in the counter-diffuser based upon the erroneous description. By extending these collisions across the entire cipher state, they were able to explore various attack scenarios. We prove that the correction of the typographical error removes all the exploitable collisions in the counter diffuser during key and IV loading operations; thereby establishing that the Joux-Reinhard attacks are an artefact of the erroneous description. Complete test vectors are included.

Note: The need to correct a single digit typographical error in the original eSTREAM Phase II submission for VEST is acknowledged by Synaptic Laboratories Limited (the owner of intellectual property in the VEST cipher and the VEST trade mark).