On the Linkability of Two Schnorr Type ID-Based Blind Signature Schemes

As a special anonymous signature, the blindness of blind signatures is an important property which distinguishes from the other signatures. And it makes it play an important role in electronic commerce. Recently, Huang et. al proposed several Schnorr Type ID-based blind signature schemes and claimed that these schemes were secure. Unfortunately, in the paper, we discuss the security of the first scheme and the three scheme of Huang et.al´s schemes. And the result shows that the two blind signature schemes are insecure. They exist a common flaw: linkability. Namely, they don´t satisfy the blindness of blind signature. That is to say, the signer is able to link a valid message-signature pair obtained by some user. Finally, we give the corresponding attack on the two schemes and reason analysis to produce such attack.