Cryptology ePrint Archive: Report 2020/1005

Trouble at the CSIDH: Protecting CSIDH with Dummy-Operations against Fault Injection Attacks

Fabio Campos and Matthias J. Kannwischer and Michael Meyer and Hiroshi Onuki and Marc Stöttinger

Abstract: The isogeny-based scheme CSIDH is a promising candidate for quantum-resistant static-static key exchanges with very small public keys, but is inherently difficult to implement in constant time. In the current literature, there are two directions for constant-time implementations: algorithms containing dummy computations and dummy-free algorithms. While the dummy-free implementations come with a 2x slowdown, they offer by design more resistance against fault attacks. In this work, we evaluate how practical fault injection attacks are on the constant-time implementations containing dummy calculations. We present three different fault attacker models. We evaluate our fault models both in simulations and in practical attacks. We then present novel countermeasures to protect the dummy isogeny computations against fault injections. The implemented countermeasures result in an overhead of 7% on the Cortex-M4 target, falling well short of the 2x slowdown for dummy-less variants.

Category / Keywords: implementation / Isogeny-based Cryptography, CSIDH, Fault Injection Attack, Fault Resistant Implementation

Original Publication (in the same form): FDTC 2020

Date: received 19 Aug 2020

Contact author: campos at sopmac de,matthias@kannwischer eu,michael meyer@hs-rm de,onuki@mist i u-tokyo ac jp,marc stoettinger@gmail com

Available format(s): PDF | BibTeX Citation

Version: 20200819:105534 (All versions of this report)

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