An Efficient and Parallel R-LWE Cryptoprocessor

Lattice-based cryptography (LBC) is a promising and efficient public key cryptography scheme whose theoretical foundation usually lies in Learning with Error (LWE) problem and its variant such as Ring-LWE (R-LWE) is the most studied cryptosystem which allows for more efficient implementation while maintaining the hardness of an original problem. Polynomial multiplication is the bottleneck of R-LWE, that can either be done using Number Theoretic Transform (NTT) or schoolbook polynomial multiplication (SPM) algorithm. The use of SPM is wider and possible for all parameters of R-LWE schemes. This brief proposes an efficient and parallel strategy for SPM in R-LWE; by successfully reducing its time complexity from n^{2} to n^{2}/4 (making it 1.8\times faster and 1.4\times hardware efficient). Furthermore, by adjusting the bit width for the error terms, the polynomial multiplication and addition blocks are reused for both encryption and decryption modules resulting in 14% reduced area and 1.7\times better throughput in comparison to state-of-Art SPM based R-LWE designs.