Analysis of Sun et al.’s linkability attack on some proxy blind signature schemes

The proxy blind signature scheme allows the designated proxy signer using the proxy secret key to generate a blind signature on behalf of the original signer. Tan et al. presented the DLP-based and ECDLP based blind signature schemes. Awasthi and Lal proposed a improved DLP-based scheme later. Recently, Sun et al. presented linkability attack on Tan et al.’s and Awasthi–Lal’s proxy blind signature schemes respectively. In this paper, we show that Sun et al.’s attack is failed and these schemes are still satisfy the unlinkability property.