FIX: potential non-constant time division in Kyber#3846
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Some compilers generate a non-constant time division operation for the division by KyberConstants::Q. Fix is based on the patch in the reference implementation: pq-crystals/kyber@dda29cc Found and initially reported by Goutam Tamvada, Karthikeyan Bhargavan, and Franziskus Kiefer of @cryspen. Independently reported by djb as "Kyberslash". fixes #3844 Co-Authored-By: Fabian Albert <fabian.albert@rohde-schwarz.com> Co-Authored-By: Amos Treiber <amos.treiber@rohde-schwarz.com>
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Given 3.3.0 is coming out in a few weeks and this is just a side channel I don't see any real need to backport. Keep in mind we only support the latest release in any series. If someone wants to pull this they can always cherry pick it. |
randombit
approved these changes
Dec 19, 2023
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Some compilers generate a non-constant time division operation for the division by
KyberConstants::Q.Fix is based on the patch in the reference implementation: pq-crystals/kyber@dda29cc
Thanks @xvzcf for reporting this.
@randombit we'll also open a pull request on against the 3.2.0 release.
closes #3844
References: