Recently, a broadcasting multiple blind signature scheme based on quantumteleportation has been proposed for the first time. It is claimed to haveunconditional security and properties of quantum multiple signature and quantumblind signature. In this paper, we analyze the security of the protocol andshow that the signatory Ui can learn the signed message m by a single particlemeasurement and the signed message m can be modified at random by anyoneaccording to the scheme. Furthermore, there are some participant attacks andexternal attacks existing in the scheme. Finally we present an improvedprotocol and show that the improved scheme can resist all of the mentionedattacks. Meanwhile, the secret keys can be used again and again, which willmake it more efficient and practical.
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