of a proxy blind signature scheme based on DLP. Journal of Software, 2005,16(5):911−915. Abstract: Proxy signature allows an original signer to delegate his/her signing capability to a proxy signer such that the proxy signer can sign messages on behalf of the original signer. Blind signature allows a user to have a given message signed by the signer without revealing any information about the message. By using Schnorr blind signature, Tan et al. recently proposed a digital proxy blind signature

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... scheme. They claimed that it satisfies the security properties of both blind signatures and proxy signatures. However, it is not the fact. This paper shows that the proposed scheme is vulnerable to universal forgery as well as linkability attacks. It also explains why their proofs of the security are incorrect. WANG Shu-Hong was born in 1977. He is a Ph.D. candidate at the School of Mathematical Sciences, Peking University. His current research areas are protocol design and analysis in information security, network security and cryptography. WANG Gui-Lin, born in 1968, is a Ph.D. candidate and research scientist. His main research areas are foundation and application of cryptography. BAO Feng is a Principal Scientist and the Head of the Cryptography Lab of the Institute for Infocomm Research in Singapore. His research areas are algorithm, authomata theory, complexity, cryptography, distributed computing, fault tolerance, and information security. WANG Jie was born in 1956. He is a professor at the School of Mathematical Sciences, Peking University. His current research areas are group theory, algebraic graph theory and cryptology.