ShiftHub: Enabling Atomic, Unlinkable, and Practical m ~1 Cross-Chain Transfer

Cross-chain transfer significantly enhances asset management among multiple blockchains. While existing cross-chain transfer schemes facilitate transferring asset ownership of users between a source blockchain and a target blockchain, they do not consider a complex scenario involvingmsource blockchains and one target blockchain (termedm∼1 cross-chain transfer). Furthermore, the variants of existing schemes for this scenario fail to concurrently achieve atomicity, unlinkability, and practical properties such as transaction aggregability, and non-collateralization, posing substantial limitations. To bridge this gap, we propose ShiftHub, the firstm∼1 cross-chain transfer scheme that simultaneously fulfills the above desired properties. ShiftHub guarantees atomicity and transaction aggregability by integratingexchange protocolswith a novelt-message-clustered redeem protocol. Unlinkability is achieved by additionally incorporating commonly used assumptions such as fixed-amount transfers, while the need for sender collateralization is eliminated by enabling the reuse of locked assets. Compatible with any blockchains that employadaptor signaturesorBLS signaturesfor transaction authentication, ShiftHub requires only signature verification and timelock functionalities on chain, ensuring near-universal blockchain compatibility. We formally prove the security of ShiftHub under static corruption using the universal composability framework. Extensive evaluation shows that ShiftHub offers superior performance over the existing scheme variant with the closest underlying protocols to ShiftHub, in terms of both off-chain and on-chain overhead, when completingm∼1 cross-chain transfer. Particularly, ShiftHub reduces the number of required transactions by (2m− 1)/3m.