WIP: Constant-flow open #764
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ct_sel_int32 in mldsa-native previously had a precondition that the condition is either 0 or 0xFFFFFFFF. This is different from mlkem-native where any value is permitted for mlk_ct_sel_int16. This commit aligns ct_sel_int32 with mlkem-native. Signed-off-by: Matthias J. Kannwischer <matthias@kannwischer.eu>
In the very end of verify one has to compare the input challenge to the re-computed challenge. If they are equal (and some previous checks on h and z passed), the signature is valid. Currently, our constant-time tests do not declassify the message and we, hence, need to declassify in this final step. Before thi commit, the declassification would happen on the recomputed challenge just before the memcmp. Now that a constant-time memcmp was added in #714, we might as well use that; that plus a constant-time selections allows us to not use any declassifications in verification, i.e., we do not leak the verification result through timing. Signed-off-by: Matthias J. Kannwischer <matthias@kannwischer.eu>
Signed-off-by: Matthias J. Kannwischer <matthias@kannwischer.eu>
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