Fan and Lei proposed an user efficient blind signature scheme based on quadratic residues. The main merit of this scheme is that only a few number of arithmetic modular operations are required for a user to get a legal signature. Therefore, it is very suitable for commerce applications. However, Shao pointed out that this scheme did not achieve the unlinkability property. Furthermore, he also proposed an improved blind signature scheme to remedy this weakness and reduce the computations for requests. In this article, we presents a linking strategy to show that this improved version is also not a true blind signature scheme.
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