Paper 2015/724 Original: eprint.iacr.org/2015/724 ↗

A masked ring-LWE implementation

Abstract

Lattice-based cryptography has been proposed as a postquantum public-key cryptosystem. In this paper, we present a masked ring-LWE decryption implementation resistant to first-order side-channel attacks. Our solution has the peculiarity that the entire computation is performed in the masked domain. This is achieved thanks to a new, bespoke masked decoder implementation. The output of the ring-LWE decryption are Boolean shares suitable for derivation of a symmetric key. We have implemented a hardware architecture of the masked ring-LWE processor on a Virtex-II FPGA, and have performed side channel analysis to confirm the soundness of our approach. The area of the protected architecture is around $2000$ LUTs, a $20\%$ increase with respect to the unprotected architecture. The protected implementation takes $7478$ cycles to compute, which is only a factor $\times2.6$ larger than the unprotected implementation.