Affiliations: School of Computer Science and Engineering, University
of Electronic Science and Technology of China, Chengdu 610054, Sichuan, P.R.
China. E-mail: fagenli@mail.xidian.edu.cn | Key Laboratory of Computer Networks and Information
Security, Xidian University, Xi'an 710071, Shaanxi, P.R. China
Abstract: In 2006, Pomykala and Barabasz [Fundamenta Informaticae 69 (2006)
411–425] proposed an elliptic curve based threshold proxy signature scheme
which requires shorter cryptographic keys. They claimed that their scheme
satisfies the secrecy, the proxy protected, the unforgeability, the
non-repudiation, and the known signers. However, in this paper, we show that
their scheme cannot achieve the proxy protected, the unforgeability and the
non-repudiation by demonstrating a conspiracy attack. In this attack, any t
malicious proxy signers can collusively impersonate some other proxy signers to
generate proxy signatures.
