Cache-Collision Timing Attacks Against AES

Overview

This paper describes several novel timing attacks against the common table-driven software implementation of the AES cipher. The authors define a general attack strategy using a simplified model of the cache to predict timing variation due to cache-collisions in the sequence of lookups performed by the encryption. The attacks presented should be applicable to most high-speed software AES implementations and computing platforms, the authors have implemented them against OpenSSL v. 0.9.8.(a) running on Pentium III, Pentium IV Xeon, and UltraSPARC III+ machines. While the task of defending AES against all timing attacks is challenging, a small patch can significantly reduce the vulnerability to these specific attacks with no performance penalty.