Adaptor Signatures An adaptor signature is a modification of a Schnorr signing protocol: instead of producing a complete signature, the signer produces a pre-signature that is invalid on its own but becomes valid once adapted with a secret value . Two key properties: 1. Witness extractability — given a complete sig and the pre-signature, anyone can compute . 2. Atomicity — observing one side of a swap reveals the secret needed for the other side. Schnorr-based adaptor (BIP340) Standard Schnorr sig: Adaptor variant with adaptor point : But the verifier checks against , not . So alone fails ver…