Cryptanalysis of Two Pairing-Based Blind Signature Schemes

Blind signatures allow the user to obtain a signature of a message in a way that the signer learns neither the message nor the resulting signature. Proxy blind signature schemes enable a proxy signer to sign message blindness on behalf of an original signer. Blind signatures can be used in cryptographic applications such as digital watermark, electronic voting and electronic cash systems. All blind signatures should satisfy the security requirement of unforgeability. In this paper, we show that Liao et al.´s pairing-based blind signature scheme is universally forgeable and Li´s ID-based proxy blind signature scheme from pairings is insecure against the original signer´s forgery.