Cryptanalysis of Li et al.’s Proxy Signature Scheme

This work shows that the security improvement of Li et al. for Park and Lee’s nominative proxy signature scheme is still insecure against the original signer’s forgery. The problem within Li et al. scheme is that the verifier cannot judge the correctness of the parameter generated by the original signer from the received signature. Key-Words: digital signature, authentication, hash function, discrete logarithm