std.crypto.kem.kyber: mitigate KyberSlash #18316
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/cc @bwesterb |
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Note that, while unlikely, this still permits the compiler to detect that the code is equivalent to a division, and lower to a division. Proper solution will be #1776. Although we don't have a fully specified proposal, I have marked that issue as "accepted" meaning that implementing such a feature blocks the release of Zig 1.0. |
andrewrk
requested changes
Dec 19, 2023
bwesterb
reviewed
Dec 20, 2023
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lgtm, thanks. |
On some architectures, including AMD Zen CPUs, dividing a secret by a constant denominator may not be a constant-time operation. And most Kyber implementations, including ours, could leak the hamming weight of the shared secret because of this. See: https://kyberslash.cr.yp.to Multiplications aren't guaranteed to be constant-time either, but at least on the CPUs we currently support, it is.
RossComputerGuy
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Jan 6, 2024
On some architectures, including AMD Zen CPUs, dividing a secret by a constant denominator may not be a constant-time operation. And most Kyber implementations, including ours, could leak the hamming weight of the shared secret because of this. See: https://kyberslash.cr.yp.to Multiplications aren't guaranteed to be constant-time either, but at least on the CPUs we currently support, it is.
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On some architectures, including AMD Zen CPUs, dividing a secret by a constant denominator may not be a constant-time operation.
And most Kyber implementations, including ours, could leak the hamming weight of the shared secret because of this. See:
https://kyberslash.cr.yp.to
Multiplications aren't guaranteed to be constant-time either, but at least on the CPUs we support, they are.