Parallel (Probable) Lock-Free Hash Sieve: A Practical Sieving Algorithm for the SVP

In this paper, we assess the practicability of Hash Sieve, a recently proposed sieving algorithm for the Shortest Vector Problem (SVP) on lattices, on multi-core shared memory systems. To this end, we devised a parallel implementation that scales well, and is based on a probable lock-free system to handle concurrency. The probable lock-free system, implemented with spin-locks, in turn implemented with CAS operations, becomes likely a lock-free mechanism, since threads block only when strictly required and chances are that they are not required to block. With our implementation, we were able to solve the SVP on an arbitrary lattice in dimension 96, in less than 17.5 hours, using 16 physical cores. The least squares fit of the execution times of our implementation, in seconds, lies between 2(0.32n -- 15) or 2(0.33n -- 16). These results are of paramount importance for the selection of parameters in lattice-based cryptography, as they indicate that sieving algorithms are way more practical for solving the SVP than previously believed.