Zhi-Kai Zhang’s research while affiliated with National Sun Yat-sen University and other places

In this paper, we present two schemes for embedding multiple subliminal messages into one-time signature schemes (OTSSs) proposed by Lamport (1971, 1981) [35,36]. Our schemes have the advantage that the subliminal receivers cannot forge a valid signature since they do not share the signer’s secret key. Our schemes can also provide more than one independent subliminal message, and the numbers of subliminal messages and receivers are larger than that of the subliminal messages in previous schemes.

Due to low-computation cost and convenient portability, smart cards are usually adopted to store the personal secret information of users for remote authentication. Although many remote authentication schemes using smart cards have been introduced in the literatures, they still suffer from some possible attacks or cannot guarantee the quality of performance for smart cards. In this paper, we classify the security criteria of remote authentication and propose a new remote login scheme using smart cards to satisfy all of these criteria. Not only does the proposed scheme achieve the low-computation requirement for smart cards, but also it can withstand the replay and the offline dictionary attacks as well. Moreover, our scheme requires neither any password table for verification nor clock synchronization between each user and the server while providing both mutual authentication and the uniqueness of valid cards.

Fair blind signatures have been widely adopted to construct untraceable electronic cash systems for dealing with the misuse of the cash. In a fair blind signature scheme, a judge can retrieve the link information in the blind signatures when the electronic cash is misused. In the design of a fair blind signature, an on-line judge must involve in every signature. Although it can provide higher security than an off-line judge, it is inefficient and is impractical to implement. In this paper, we propose a fair blind signature scheme with tamper-resistant devices, called observers. The observer can reduce the workload of the on-line judge without compromising the security of the scheme. Moreover, our scheme provides both signature-tracing and owner-tracing mechanisms, and the tracing mechanisms satisfy the nonrepudiation property. That is, the judge in our scheme can prove when and by whom the blind signature was requested. Our scheme can also withstand the chosen-message attacks since the sender cannot fully control the contents of the message-signature pair.