Slicing Up a Perfect Hardware Masking Scheme

Masking is a side-channel countermeasure that randomizes side-channel leakage, such as the power dissipation of a circuit. Masking is only effective on the condition that the internal random mask remains a secret. Previous research has illustrated how a successful estimation of the mask bit in circuit level masking leads to successful side-channel attacks. In this paper, the authors extend this concept to algorithmic masking, which uses multi-bit masks. The key observation is that the power dissipation of a masked circuit and the mask value are not independent. They exploit this property by using a slice of the power samples obtained by partial selection.