Abstract: The identity-based ring signcryptions have both high efficiency of identity-based cryptosystem and signcryption technology and the ambiguity of ring signature. In the fair exchange protocol based on signcryption proposed by Luo, et al (Luo M, Zou C H, Hu J, 〖WTBX〗et al.〖WTBZ〗Signcryption-based fair exchange protocol. Journal of Communications, 2010, 31(8A): 146-150), the fairness and efficiency are not good enough. The new scheme introduced a more efficient identity-based ring signcryption and dealt with the decryption and the signature-and-identity binding separately. A new fair exchange protocol was proposed based on this new scheme. The analysis shows that this scheme overcomes the fairness defect of the original scheme and has a better efficiency, which makes it a good application in electronic payment and contract signing.

Key words: identity-based, ring signcryption, concurrent signature, fair exchange protocol, fairness

摘要： 基于身份的环签密算法兼具基于身份的密码体制与签密技术高效性的优点，同时具备环签名的模糊性。针对罗铭等提出的基于签密的公平交换协议(罗铭，邹春华，胡军，等. 基于签密的公平交易协议. 通信学报，2010，31(8A)：146-150)中公平性水平与算法效率不高的问题，新方案引入了一个更加高效的基于身份的环签密算法，并将绑定签名身份与解密密文分开处理，构造了一种新的并发签名方案，并基于该方案构造了一个公平交换协议。分析表明，该方案克服了原方案公平性的不足，并在算法效率上有所提高，能很好地应用在电子支付、合同签署等电子商务活动中。

关键词: 基于身份, 环签密, 并发签名, 公平交易协议, 公平性