Improved progressive BKZ algorithms and their precise cost estimation by sharp simulator.

*(English)*Zbl 1385.94007
Fischlin, Marc (ed.) et al., Advances in cryptology – EUROCRYPT 2016. 35th annual international conference on the theory and applications of cryptographic techniques, Vienna, Austria, May 8–12, 2016. Proceedings. Part I. Berlin: Springer (ISBN 978-3-662-49889-7/pbk; 978-3-662-49890-3/ebook). Lecture Notes in Computer Science 9665, 789-819 (2016).

Summary: In this paper, we investigate a variant of the BKZ algorithm, called progressive BKZ, which performs BKZ reductions by starting with a small blocksize and gradually switching to larger blocks as the process continues. We discuss techniques to accelerate the speed of the progressive BKZ algorithm by optimizing the following parameters: blocksize, searching radius and probability for pruning of the local enumeration algorithm, and the constant in the geometric series assumption (GSA). We then propose a simulator for predicting the length of the Gram-Schmidt basis obtained from the BKZ reduction. We also present a model for estimating the computational cost of the proposed progressive BKZ by considering the efficient implementation of the local enumeration algorithm and the LLL algorithm. Finally, we compare the cost of the proposed progressive BKZ with that of other algorithms using instances from the Darmstadt SVP Challenge. The proposed algorithm is approximately 50 times faster than BKZ 2.0 (proposed by Chen-Nguyen) for solving the SVP Challenge up to 160 dimensions.

For the entire collection see [Zbl 1339.94004].

For the entire collection see [Zbl 1339.94004].