  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.
