Short Group Signatures with Controllable Linkability

In this paper, we present a short group signature scheme for dynamic membership with controllable link ability. The controllable link ability enables an entity who possesses a special linking key to check if two signatures are from the same signer while preserving anonymity. It can be used for various anonymity-based applications that require necessarily the link ability such as vehicular adhoc network, and privacy-preserving data mining. Our scheme is sufficiently efficient and so, well-suited for real-time applications even with restricted resources, such as vehicular adhoc network and Trusted Platform Module. We prove that it achieves anonymity, trace ability, and non-frame ability. Our scheme supporting controllable link ability yields a signature that is shorter than the best-known normal group signature by one group element. Furthermore, we show by experiment that our scheme is comparable to the group signature scheme in terms of the amount of computation for basic operations such as signing, verification, and the key update caused by revocation. Using the link ability for dynamic membership, computation overhead in opening signer's identity can be significantly reduced.