最近，谷等人提出了一種具有無需可信第三方的匿名代理簽名方案, 即在代理簽名中
可以隱藏代理簽名者的身份, 并且驗證者無法從代理簽名中識別代理者身份, 在出現爭議
時, 驗證者可以通過原始簽名者揭示代理簽名者的身份. 然而, 根據安全性分析, 可知在谷
等人提出的方案中原始簽名者可以偽造所有代理簽名人的代理簽名密鑰, 并在委任書中任
意偽造代理人的身份, 從而原始簽名人可以偽造代理簽名, 而代理簽名人也因此會否認自
己的代理簽名. 因此, 谷等人給出匿名代理簽名方案并不安全. 最后，指出無需可信第三方
匿名代理簽名方案不能實現的內在原因.
關鍵詞：簽名，數字簽名，代理簽名， 匿名性
Abstract. Recently, an anonymous proxy signature scheme without third trusted party was
proposed by Gu et al, where the proxy signer’s identity is anonymous in the proxy signature, and the signature verifier cannot derive the proxy signer’s identity from the proxy signature. In the case of a later dispute, the verifier can reveal the real identity of the proxy signer from the proxy signature. However, according to our security analysis to this scheme, it is found that the original signer can forge all the proxy signers’ proxy secret keys, and the original signer can forge the identities of the proxy signers too. So, the original signer can forge the proxy signatures of any of the proxy signers, and the proxy signers will deny the signatures signed by themselves. Therefore, the anonymous proxy signature scheme proposed by Gu et at. is not secure. At last, the reasons for the failure of such scheme is present.
Keyword. signature, digital signature, proxy signature, anonymity