Study on designated verifier proxy signature schemes with provable security

This Proxy signature has been one of the hot spot in cryptography research as it can delegate the signing right of the original signer to the proxy signer. Therefore, it is applied in many areas such as mobile networks, distributed systems, control systems and other some information systems. Recently, many proxy signature schemes with special properties have been proposed. However, most of them is been proved to be insecure or inefficient. In this paper, we study two efficient proxy signature schemes proposed recently with special property, i.e. blind property and designated verifier property respectively. We point out that there exist some security drawbacks in the both schemes, including the replace problem of delegation warrant, the forgeability problem from the proxy signer and the forgability problem from the normal user. In order to overcome these problems, we propose a solution method for each scheme. Thus, these both improved schemes are securer than original both schemes, which makes them more suitable for applying.