Paper 2020/972
Optimized Binary GCD for Modular Inversion
Thomas Pornin
Abstract
In this short note, we describe a practical optimization of the well-known extended binary GCD algorithm, for the purpose of computing modular inverses. The method is conceptually simple and is applicable to all odd moduli (including non-prime moduli). When implemented for inversion in the field of integers modulo the prime $2^{255}-19$, on a recent x86 CPU (Coffee Lake core), we compute the inverse in 6253 cycles, with a fully constant-time implementation.
Metadata
- Available format(s)
-
PDF
- Category
- Implementation
- Publication info
- Preprint. MINOR revision.
- Keywords
- binary GCDmodular inversion
- Contact author(s)
- thomas pornin @ nccgroup com
- History
- 2020-08-23: last of 2 revisions
- 2020-08-18: received
- See all versions
- Short URL
- https://ia.cr/2020/972
- License
-
CC BY
BibTeX
@misc{cryptoeprint:2020/972,
author = {Thomas Pornin},
title = {Optimized Binary {GCD} for Modular Inversion},
howpublished = {Cryptology {ePrint} Archive, Paper 2020/972},
year = {2020},
url = {https://eprint.iacr.org/2020/972}
}
