Security of Adaptor Signatures in Parallel Signing

This article by AdamISZ, currently a draft and unreviewed note, delves into the security properties of ’signature adaptors’ in the context of Schnorr signatures and MuSig protocols. The study begins with definitions and explores the practicality and security of using these adaptors in multiple signing sessions. The key point is that adaptor signatures can be securely used in conjunction with MuSig, ensuring the non-forgeability of signature fragments even when the same adaptor point is used in parallel sessions. The article also reviews prior work, such as that by Poelstra, Fournier, and Aumayr, highlighting their contributions and limitations. The practical implications of this study are significant for applications like CoinSwap and anonymous multi-hop locks, where adaptor signatures are crucial. The article concludes that while single public key adaptors are generally ’useless’ due to their inability to enforce secret value revelation, they play a critical role in multi-party scenarios.