[rom] Introduce domain separation prefix for SPHINCS+. #23762
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cfrantz
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moidx
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| * | ||
| * In our case, `ctx` is always the empty string, so the length is 0. | ||
| */ | ||
| static const uint8_t kSpxVerifyPureDomainSep[] = { |
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This sgtm. The sequence of three arguments gets reduced to two due to len(ctx) == 0. This matches the proposed specification.
For later compatibility with the FIPS 205 standard, introduces a domain separation prefix for the message that is always two zero bytes, indicating a "pure" (not pre-hashed) message and an empty context. Signed-off-by: Jade Philipoom <[email protected]>
Signed-off-by: Jade Philipoom <[email protected]>
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For later compatibility with the FIPS 205 standard, introduces a domain separation prefix for the message that is always two zero bytes, indicating a "pure" (not pre-hashed) message and an empty context. For now, the pre-hashed variant is not supported (we may add it as a separate change, but it made sense to me to do this step first).
I chose to implement the domain separator outside of the main SPHINCS+ implementation to maintain KAT compatibility; the existing KATs don't include the domain separator, and NIST has said that their KATs will include targets for the "internal" underlying operation that does not include the prefix.
Resolves #21944