Affiliations: Department of Information Management, and Graduate
Institute of Networking and Communication Engineering, Chaoyang University of
Technology, 168 Gifeng E. Rd., Wufeng, Taichung County, Taiwan 413,
R.O.C. | Department of Computer and Information Science,
National Chiao-Tung University, 1001 Ta Hsueh Road, Hsinchu, Taiwan,
R.O.C. | Department of Computer Science and Information
Engineering, TamKang University, Tamsui, Taipei Hsien,251,Taiwan, R.O.C.
Abstract: Recently, Hwang and Shi proposed an efficient proxy signature scheme
without using one-way hash functions. In their scheme, an original signer
needn't send a proxy certificate to a proxy signer through secure channels.
However, there are two public key substitution methods that can be used to
attack their scheme. In this article, we show that their scheme is vulnerable
to the public key substitution attacks.
Keywords: cryptography, digital signature, one-way hash function, proxy signatures
