Mitigating cache contention-based attacks by logical associativity

Many cache designs have been proposed to guard against last-level cache, contention-based, side-channel attacks. One of the most well-known implementations, CEASER-S, applies an encryption cypher with a periodically changing key as a cache indexing function. By increasing the re-keying frequency, CEASER-S can defeat an attack. However, this can lead to performance degradation. In this paper, we propose cache logical associativity. By combining this approach with CEASER-S, our cache, CEASER-SH, sacrifices less performance while maintaining the same security level against more advanced contention-based side-channel attacks. For example, compared with CEASER-S, CEASER-SH with a logical associativity of 3 can reduce the miss rate degradation by about 30% and that of the CPI by 1% while maintaining the same security level against a strong Prime+Probe attack.