In recent years, the confidentiality of smart contracts has become a fundamental requirement for practical applications. While many efforts have been made to develop architectural capabilities for enforcing confidential smart contracts, a few works arise to extend confidential smart contracts to Multi-Party Computation (MPC), i.e., multiple parties jointly evaluate a transaction off-chain and commit the outputs on-chain without revealing their secret inputs/outputs to each other. However, existing solutions lack public verifiability and require O(n) transactions to enable negotiation or resist adversaries, thus suffering from inefficiency and compromised security. In this paper, we propose Cloak, a framework for enabling Multi-Party Transaction (MPT) on existing blockchains. An MPT refers to transitioning blockchain states by an publicly verifiable off-chain MPC. We identify and handle the challenges of securing MPT by harmonizing TEE and blockchain. Consequently, Cloak secures the off-chain nondeterministic negotiation process (a party joins an MPT without knowing identities or the total number of parties until the MPT proposal settles), achieves public verifiability (the public can validate that the MPT correctly handles the secret inputs/outputs from multiple parties and reads/writes states on-chain), and resists Byzantine adversaries. According to our proof, Cloak achieves better security with only 2 transactions, superior to previous works that achieve compromised security at O(n) transactions cost. By evaluating examples and real-world MPTs, the gas cost of Cloak reduces by 32.4% on average.
翻译:近些年来,智能合同的保密性已成为实际应用的基本要求; 智能合同的保密性已成为智能合同的一项基本要求; 虽然已作出许多努力发展执行保密智能合同的建筑能力; 但也出现了一些工作,将保密智能合同扩大到多党计算(MPC),即多个当事方共同评价一项交易的离链交易,并在不相互透露其秘密投入/产出的情况下在链上执行产出; 然而,现有的解决办法缺乏公开的可核查性,要求O(n)交易能够谈判或抵制对手,从而造成效率低下和安全受损; 在本文件中,我们提议建立Cloak,即一个使多党交易(MPT)得以在现有的链上执行保密智能合同(MPT)的框架; MPT 是指通过一个可公开核查的离链的离链(MPC)。 我们通过协调TEE和链,确定并处理MPT在链上产出的挑战。 因此,Cloak保障了离链的谈判进程(一个当事方在不知道身份或当事方总数的情况下加入MPT提案,在MPT提案解决之前), 实现公共核查(公众可以确认MPT4) 将M/Dreval交易的正确处理成本, 并改进了我们的安全交易, 安全记录。