Abstract: Blind signature allows a user to obtain signatures from an authority on any document, in such a way that the authority learns nothing about the message that is being signed. In partially blind signatures, the signer can explicitly include some agreed common information such as the expiration date and the face value in the blind signature. The blindness is an important property in blind signature scheme. In this work, we analyze security of Huang et al�s convertible undeniable partially blind signature scheme and show that the scheme doesn�t satisfy blindness, in other words, the signer is able to link a valid message-signature pair obtained by some user. It means that the blind signature scheme is not secure.