Draft Bitcoin proposal BIP461 defines a common ECDSA signing procedure to make deviations that could conceal key leakage easier to detect. Independent compliant signers should produce identical signatures for the same secret key and message hash. Comparison requires another independent signer to access the secret key, and a mismatch cannot by itself establish theft. The proposal requires no Bitcoin consensus change, but a malicious signer could pass a test and leak secrets on a different transaction.