Improved Endorsed E-Cash System with DAA-A

At present, the existing endorsed e-cash system has a low communication efficiency, and its fair exchange protocol employs inefficient cut-and-choose proofs. In addition, the centralized TTP (trusted third party) is vulnerable to denial-of-service attacks. So far, several related fair payment systems have been proposed. Unfortunately, some of them use cut-and-choose proofs, and the others adopt verifiable encryption schemes with security flaw. Inspired by the idea of self-blindable attribute-based credentials, a concrete DAA-A (direct anonymous attestation with attributes) scheme is constructed. Based on the new DAA-A scheme, an improved endorsed e-cash system is proposed, which achieves a high level of exculpability. In order to improve users’ computational efficiency in the spending process, the set-membership proof by Arfaoui et al’s is adopted, and the efficiency of user’s signature of knowledge is also optimized with the technique of pre-computation. In order to bypass the expensive cut-and-choose proof, a new optimistic fair exchange sub-protocol supporting distributed TTPs is provided. Furthermore, if combined with the Golle-Mironov model, the new system also suits for the environment of outsourcing computing. Compared with the previous similar ones, the new system meets several desirable properties simultaneously, i.e., it supports multiple payments, and does not depend on cut-and-choose proofs and allows users to be stateless, etc. What’s more, the fair exchange protocol of the new system considers the risk of denial-of-service attacks.