A fair contract signing scheme ensures that contract signing participants can fairly exchange the digital signatures of the contract, which has a wide range of applications on the Internet. Verifiable Encrypted Signature (VES) can be used as a fair exchange mechanism for digital signatures, in which it requires a centralized Trusted Third Party (TTP) as an adjudicator. However, there are many security challenges with the centralized TTP. For example, it may disclose the contents of the contract, collude with others, or even occurs a service interruption. To address those problems, in this paper, we propose a two-party fair contract signing scheme based on Ethereum smart contract, which allows participants to fairly perform the contract signing procedures on the blockchain. Specifically, we propose a modified VES scheme in which no centralized adjudicator is needed. Then we design the fair contract signing scheme based on the modified VES scheme. We leverage the Ethereum smart contract technology to ensure fairness, which has the characteristics of decentralization, verifiability, autonomy, efficiency, and tampering resistant. The theoretical analysis and experimental results show that our scheme is secure and feasible.

公平的合同签署方案可确保合同签署者可以公平地交换合同的数字签名，该数字签名在Internet上具有广泛的应用。可验证的加密签名（VES）可以用作数字签名的公平交换机制，在这种机制中，它需要集中的可信第三方（TTP）作为裁决者。但是，集中式TTP存在许多安全挑战。例如，它可能会披露合同内容，与他人合谋甚至发生服务中断。为了解决这些问题，本文提出了一种基于以太坊智能合约的两方公平合约签名方案，该方案使参与者能够在区块链上公平地执行合约签名程序。特别，我们提出了一种经过修改的VES方案，其中不需要集中裁决者。然后，基于改进的VES方案设计了公平合同签署方案。我们利用以太坊智能合约技术来确保公平，该技术具有去中心化，可验证性，自治性，效率和防篡改的特征。理论分析和实验结果表明，该方案是安全可行的。