Parallel Implementation of BDD Enumeration for LWE

One of the most attractive problems for post-quantum secure cryptographic schemes is the LWE problem. Beside combinatorial and algebraic attacks, LWE can be solved by a lattice-based Bounded Distance Decoding (BDD) approach. We provide the first parallel implementation of an enumeration-based BDD algorithm that employs the Lindner-Peikert and Linear Length pruning strategies. We ran our algorithm on a large variety of LWE parameters, from which we derive the following interesting results. First, our parallel enumeration achieves almost perfect speed-up, which allows us to provide for the first time practical cryptanalytic results on standard LWE parameters of meaningful size. Second, we conclude that lattice-based attacks perform better than recent advanced BKW-type algorithms even for small noise, while requiring way less samples. Third, we experimentally show weaknesses for a binary matrix LWE proposal of Galbraith.