archetech / archon / 24735235154

95%

main: 89%

Pull #455

github

fix(python-keymaster): normalize ECDSA signatures to low-S form

Python's cryptography library produces ECDSA signatures with either s or
n-s (~50% each). Both the TypeScript gatekeeper (@noble/secp256k1 with
default lowS: true) and the Rust gatekeeper (k256::ecdsa::Signature::from_slice
enforces canonical form) reject high-S signatures as non-canonical.

This caused the Python keymaster CI legs to fail intermittently with
'Invalid operation: proof' — any create/sign operation that happened
to produce a high-S signature was rejected.

Normalize s to the lower half of the curve order in sign_hash, matching
the @noble/secp256k1 and k256 verification contract.

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