Boolean Masking for Arithmetic Additions at Arbitrary Order in Hardware

Modular addition is an important component of many cryptographic algorithms such as ARX-ciphers and lattice-based post-quantum secure schemes. In order to protect devices that execute these algorithms against side-channel attacks, countermeasures such as masking must be applied. However, if an implementation needs to be secured against multivariate attacks, univariately secure masking schemes do not suffice. In this work, we focus on hardware architectures for higher-order masked addition circuits. We present and discuss three adder designs that are protected with a provably secure masking scheme. Concretely, we discuss Kogge–Stone, Sklansky and Brent–Kung adders regarding their suitability for high-order masking and their performance in this setting. All architectures are fully pipelined and achieve a throughput of one addition per cycle. In order to achieve multivariate security at arbitrary orders, we use HPC2 Gadgets that satisfy the PINI security notion. Additionally, we apply a first-order secure threshold implementation scheme to the adder variants and compare their performance in the univariate case.