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Use raw signatures for subtree cosignatures - #308
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lukevalenta merged 1 commit intoOct 20, 2026
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added this pull request to stack #309
October 16, 2026 15:27
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Why
Checkpoint and subtree cosignatures have different wire formats. A checkpoint cosignature carries an 8-byte POSIX timestamp prefix followed by the algorithm signature. A subtree cosignature is the raw algorithm signature and has no timestamp. Prefixing a subtree signature makes an otherwise valid
sign-subtreeresponse incompatible with implementations of the witness protocol and with certificates embedding the signature.This change emits and verifies raw 2420-byte ML-DSA-44 values for
subtree/v1, while retaining timestamp-prefixed values for checkpoint signed-note lines. The mirror worker follows the same split when responding tosign-subtree.Compatibility
Compatible with
c2sp.org/tlog-cosignature@v1.1.0subtree cosignatures andc2sp.org/tlog-witness@v1.1.0sign-subtree; both refer todraft-ietf-plants-merkle-tree-certs-07for subtree validity and consistency proofs. Checkpoint behavior remains compatible withc2sp.org/tlog-checkpoint@v1.1.0andtlog-cosignature@v1.1.0.