Narrow Results

Group signatures are typically used to authenticate the signer of message while preserving the privacy of the signer. Group signature should be minimized to reduce potential communication overhead. We propose a novel short group signature scheme that generates constant-size group public key and constant-size group signature. The scheme, using pairing-friendly elliptic curves, is efficient in construction. We give the security proof under XDH and ECDL hardness assumptions in the BMW model. Furthermore, we propose two group membership revocation methods which provide revocation information only to verifiers. One revocation method exposes partial private key of revoked users, which requires less revocation information. The other revocation method includes mixed private key information without revealing the real private keys of revoked users. This method is simple in revocation check.

With the popularization of E-payment, more and more electronic payment protocols have been proposed. In 2021, Lin et al. proposed a trusted third-party E-Payment protocol based on a set of three-particle local indistinguishable orthogonal product (X-LIOP) states. In this paper, we first point out that there is a security flaw where the merchant can forge the purchase goods information to sell something that the customer does not want to buy in Lin et al. protocol. Besides, the X-LIOP states used by Lin are not orthogonal and can be discriminated by Local Operation and Classical Communication (LOCC). Second, we propose a new electronic payment protocol that combines group signature and the three-particle X-LIOP states. Compared with Lin et al. protocol, customers can purchase goods anonymously in our protocol and the unforgeability of messages and signatures is guaranteed.

A quantum proxy group signature scheme is proposed with χ-type entangled states. Our scheme combines the properties of group signature and proxy signature. Moreover, the particles in the χ-type state sequence are used to distribute proxy warrants and quantum keys in the initial phase, and then used for quantum signature. Therefore it increases the utilization rate of quantum resources compared with the general quantum signature scheme. Finally, the unconditional security of our scheme is also analyzed.

In 1998, Lee and Chang proposed a group signature scheme based on the discrete logarithm problem. Later, the Ao-Chen-Bai group signature scheme was brought out as an improved scheme of Lee-Chang, however it was proven that could not resist forgery attack. To solve this problem, a new group signature scheme is proposed in this paper. This new scheme extends the algorithm in the Galois Field GF(p) of the original group signature scheme to the ring Z_n, and at the same time, by modifying the joining and identifying stages, so it increases the security performance and the computation efficiency. This scheme can be applied to other ring-based cryptographies schemes.

The conventional group signature scheme allows a group member to anonymously sign a message on behalf of the group, but only the group manager can identify the signer. Sometimes, a group member may send a subliminal message to the special receiver on behalf of the group, while others cannot obtain this subliminal message but can verify this signature's validity. In this paper, we extend the conventional group signature and propose a novel signature type, namely the group signature scheme with subliminal channel, to realize this functionality. In this scheme, the size of signature and public key is independent of the size of the group.