Crypanalysis of Kuo and Chen's Threshold Proxy Signature Scheme Based on the RSA

• Published in: Fourth International Conference on Information Technology (ITNG'07) pp. 815 - 818
• Main Authors: Fengying Li, Qingshui Xue, Zhenfu Cao
• Format: Conference Proceeding
• Language: English
• Published: IEEE 01.04.2007
• Subjects: Computer science; Cryptography; Digital signatures; Equations; Information security; Information technology; Mobile agents; Protection
• ISBN: 9780769527765; 0769527760
• DOI: 10.1109/ITNG.2007.61

In a (t,n) threshold proxy signature scheme, an original signer delegates a group of n proxy signers to sign messages on behalf of him or her. When the proxy signature is created, t or more proxy signers cooperate to generate valid proxy signatures and any less than t proxy signers can't cooperatively produce valid proxy signatures. In 2003, Hwang et al. proposed a practical threshold proxy signature scheme (HLL-scheme) which is based on RSA crypto system for the first time. In 2004, Wang et al. had provided some comments on HLL-scheme. They showed that some mistakes of equations had made HLL-scheme become insecure. Moreover, in 2005, Kuo and Chen also showed two security weaknesses in Hwang et al.'s scheme: one is similar to RSA reblocking problem and the other is that the value of L i is not clearly defined. In addition, to overcome the second shortcoming of HLL-scheme, Kuo and Chen also provided a modified threshold proxy signature scheme (KC-scheme) based on HLL-scheme. By observation, we find that KC-scheme cannot still work. In other words, in KC-scheme, the value of L i cannot still be worked out, as makes KC-scheme not workable. To design a workable threshold proxy signature scheme, based on KC-scheme, an improved scheme is proposed