Cryptology ePrint Archive: Report 2018/782

A faster way to the CSIDH

Michael Meyer and Steffen Reith

Abstract: Recently Castryck, Lange, Martindale, Panny, and Renes published CSIDH, a new key exchange scheme using supersingular elliptic curve isogenies. Due to its small key sizes, and the possibility of a non-interactive and a static-static key exchange, CSIDH seems very interesting for practical applications. However, the performance is rather slow. Therefore, we employ some techniques to speed up the algorithms, mainly by restructuring the elliptic curve point multiplications and by using twisted Edwards curves in the isogeny image curve computations, yielding a speed-up factor of 1.33 in comparison to the implementation of Castryck et al. Furthermore, we suggest techniques for constant-time implementations.

Category / Keywords: implementation / CSIDH , Post-Quantum Cryptography, Supersingular Elliptic Curve Isogenies

Original Publication (in the same form): INDOCRYPT 2018

Date: received 26 Aug 2018, last revised 2 Nov 2018

Contact author: michael meyer at hs-rm de

Available format(s): PDF | BibTeX Citation

Version: 20181102:122245 (All versions of this report)

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