Paper 2021/1528

An Alternative Approach for Computing Discrete Logarithms in Compressed SIDH

Kaizhan Lin, Weize Wang, Lin Wang, and Chang-An Zhao

Abstract

Currently, public-key compression of supersingular isogeny Diffe-Hellman (SIDH) and its variant, supersingular isogeny key encapsulation (SIKE) involve pairing computation and discrete logarithm computation. In this paper, we propose novel methods to compute only 3 discrete logarithms instead of 4, in exchange for computing a lookup table effciently. The algorithms also allow us to make a trade-off between memory and effciency. Our implementation shows that the effciency of our algorithms is close to that of the previous work, and our algorithms perform better in some special cases.