“Untraceability” Analysis of Two ID-Based Proxy Blind Signature from Bilinear Pairings

“Untraceability” is an important property of Proxy blind signature. Zhang proposed some new untraceable blind signatures in order to enhance the security of Cai et al. (2007) and Hu et al. (2007)’s schemes. However, this study shows there are three important conclusions: 1. By reduction, we prove that the cryptanalysis method proposed by Zhang is improper and Cai et al. (2007)’s schemes does satisfy the property of untraceability; 2. On that basis, we pinpoints a new analysis method of untraceability which has effectively proved that Hu et al. (2007)’s scheme doesn’t satisfy the property of untraceability. Furthermore, the method can be used as a standard method which could analyze other schemes related with blind signature; 3. Zhang’s scheme is unpractical since the cost of the scheme is higher compared with Cai et al. (2007)’s scheme.