A Multi-Party, Multi-Blockchain Atomic Swap Protocol with Universal Adaptor Secret

The increasing complexity of digital asset transactions across multiple blockchains necessitates a robust atomic swap protocol that can securely handle more than two participants. Traditional atomic swap protocols, including those based on adaptor signatures, are vulnerable to malicious dropout attacks, which break atomicity and compromise the security of the transaction. This paper presents a novel multi-party atomic swap protocol that operates almost entirely off-chain, requiring only a single on-chain transaction for finalization. Our protocol leverages Schnorr-like signature verification and a universal adaptor secret to ensure atomicity and scalability across any number of participants and blockchains without the need for smart contracts or trusted third parties. By addressing key challenges such as collusion attacks and malicious dropouts, our protocol significantly enhances the security and efficiency of multi-party atomic swaps. Our contributions include the first scalable, fully off-chain protocol for atomic swaps involving any number of participants, adding zero overhead to native blockchains, and providing a practical and cost-effective solution for decentralized asset exchanges.