Stateless-Recipient Certified E-Mail System Based on Verifiable Encryption
CT-RSA '02 Proceedings of the The Cryptographer's Track at the RSA Conference on Topics in Cryptology
A "Paradoxical" Indentity-Based Signature Scheme Resulting from Zero-Knowledge
CRYPTO '88 Proceedings of the 8th Annual International Cryptology Conference on Advances in Cryptology
A Family of Trusted Third Party Based Fair-Exchange Protocols
IEEE Transactions on Dependable and Secure Computing
Information Sciences: an International Journal
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In these days, the privacy of a user in information communication system is more important than ever before. Especially, the property is important for mobile communication systems due to the mobility of underlying mobile devices. Until now, many cryptographic tools have been proposed for achieving users' privacy. In this paper, we review two privacy-oriented cryptographic protocols, and show their security holes. We also provide some countermeasure to fix the weaknesses. First, we discuss the security of the user identification scheme proposed by Hsu and Chuang which permits a user to anonymously log into a system and establish a secret key shared with the system. We show that the Hsu-Chuang scheme is not secure against known session key attacks, and then we provide a countermeasure which can be used for enhancing the security the Hsu-Chuang scheme. Secondly, we review a deniable authentication proposed by Harn and Ren which protects the privacy of a message sender. Then we show that the protocol has a potential incompleteness and two weaknesses.