sign/{ed25519,ed448}: check if public key is identity.#617
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When parsing a public key or verifying a signature, check that the public key is not the identity element.
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What's the reasoning here? We can't check for all ways a public key can be weak. |
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drmikecrypto
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Jun 28, 2026
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Nice catch — accepting the identity point as a valid public key would undermine signature verification assumptions.
The IsIdentity() check in verify() is the right layer (after FromBytes succeeds but before scalar math). The test vectors covering Verify, VerifyPh, VerifyWithCtx, and UnmarshalBinaryPublicKey look thorough.
One minor note: worth confirming IsIdentity() matches RFC 8032's encoding of the identity (y=1, x=0) for all code paths that ingest public keys, not just verify — but the unmarshal test already covers the scheme entry point.
LGTM from a security perspective.
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When parsing a public key or verifying a signature, check that the public key is not the identity element.