[crypto] P256 scalar multiplication code-review for SCA hardening #27771
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Avoid potential horizontal SCA issue in P256 scalar multiplication based on code review. Avoid that source and dest of one case in BN.SEL uses the same value by preseting with randomness. Re-order code to randomize destination of (first) BN.SEL before 1st use. Typos and minor edits of comments in P256 scalar mult. Signed-off-by: Johann Heyszl <[email protected]>
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h-filali
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andrea-caforio
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andreaskurth
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Closing and re-opening to enable merge queue for this PR (which was created before MQs were enabled -- see Slack) |
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Avoid potential horizontal SCA issue in P256 scalar multiplication based on code review. Avoid that source and dest of one case in BN.SEL uses the same value by preseting with randomness.
Runtime overhead +3*320 instructions = very low.
Codesize overhead +3 instruction = very low.