Detection of security protocols with XOR by improving Scyther

Scyther is an effective tool for security protocol analysis, however it cannot support such protocols with XOR operation mainly due to the decryption unifier(DU) problem. Many security protocols fundamentally depend on the algebraic properties of XOR operators. In this paper, we improve the procedure of DU by making Scyther have the ability of XOR operation in state extension. Meanwhile, and use constraint solving method to compute the attacking XOR terms by generating the type constraints, domain constraints and equation constraints. Based on this method, we successfully detect an attack of NSPK-XOR protocol.