Improved Fair Exchange Protocol Based on Signcryption-Based Concurrent Signature

摘要

Through analysis, we point out Luo et al.’s andSun et al.’s signcryption-based concurrent signatureschemes have the same defect in ambiguity and therefore thefair exchange protocols based on their schemes are not fair.Thus based on the notions of signcryption and concurrentsignature, a new signcryption-based concurrent signaturescheme from bilinear pairing is presented, and based on thisscheme, a new fair exchange protocol is proposed. Since weadopt a new method to construct the newsigncryption-based concurrent signature scheme, the newscheme redresses the flaw of Luo et al.’s and Sun et al.’sschemes, and the fair exchange protocol based on the newscheme is also fair. Besides, due to the new scheme’sindependence of the ring signature and simplification ofencryption operations, the new scheme has the advantage ofshort signatures and low computation cost. We improve Luoet al.’s definition of the security model of asigncryption-based concurrent signature scheme and provethe proposed scheme and protocol are secure under thecomputational Diffie-Hellman assumption in the randomoracle model.