Informatica

Since threshold proxy signature has been proposed, all threshold proxy signature schemes are based on the discrete logarithm problems in the modular multiplicative group which has an element g with a large prime order. Nowadays this kind of threshold proxy signature schemes become more and more complex and time-consuming for security and specific requirement. In this paper, we propose a (bilinear) pairing-based threshold proxy signature scheme with known signers, analyze its security and check the following properties the proposed scheme has: non-repudiation, unforgeability, identifiability, distinguishability, verifiability, prevention of misuse of proxy signing right, etc. Moreover, we point out that the proposed scheme is of great efficiency by comparing it with Sun’s and Hsu et al.’s scheme.

In 1995, Wu proposed a remote login authentication scheme based on geometric approach. However, Chien, Jan and Tseng presented a cryptanalysis of Wu’s scheme to show that it is not secure. Moreover, they proposed a modified version of Wu’s scheme. This paper presents there is a serious weakness in this modified remote login authentication scheme. We show that an illegal user can easily forge a valid login request in the modified version proposed previously.

Recently, Sun proposed a private-key encryption scheme based on the product codes with the capability of correcting a special type of structured errors. In this paper, we present a novel method to improve the information rate of Sun's scheme. This method uses the added error vector to carry additional information. Some information bits are mapped into an error vector with the special structure to be added to a codeword. Once the error vector can be identified, the additional information can be recovered.

This paper discusses a known-plaintext attack on a redundancy reducing cipher method which is proposed by Wayner. We also propose an extension of Wayner's redundancy reducing cipher scheme so that the security will be improved greatly.

Recently, Harn proposed an efficient scheme that can batch verification multiple RSA digital signatures. His scheme can reduce signature verification time. However, there is a weakness in his scheme. In this study, we present two methods to against his scheme.