Paper 2015/105

Inner Product Masking Revisited

Josep Balasch, Sebastian Faust, and Benedikt Gierlichs

Abstract

Masking is a popular countermeasure against side channel attacks. Many practical works use Boolean masking because of its simplicity, ease of implementation and comparably low performance overhead. Some recent works have explored masking schemes with higher algebraic complexity and have shown that they provide more security than Boolean masking at the cost of higher overheads. In particular, masking based on the inner product was shown to be practical, albeit not efficient, for a small security parameter, and at the same time provable secure in the domain of leakage resilient cryptography for a large security parameter. In this work we explore a security versus efficiency tradeoff and provide an improved and tweaked inner product masking. Our practical security evaluation shows that it is less secure than the original inner product masking but more secure than Boolean masking. Our performance evaluation shows that our scheme is only four times slower than Boolean masking and more than two times faster than the original inner product masking. Besides the practical security analysis we prove the security of our scheme and its masked operations in the threshold probing model.