k-Times Anonymous Authentication with a Constant Proving Cost

A k-Times Anonymous Authentication (k-TAA) scheme allows users to be authenticated anonymously so long as the number of times that they are authenticated is within an allowable number. Some promising applications are e-voting, e-cash, e-coupons, and trial browsing of contents. However, the previous schemes are not efficient in the case where the allowable number k is large, since they require both users and verifiers to compute O(k) exponentiation in each authentication. We propose a k-TAA scheme where the numbers of exponentiations required for the entities in an authentication are independent of k. Moreover, we propose a notion of public detectability in a k-TAA scheme and present an efficient publicly verifiable k-TAA scheme, where the number of modular exponentiations required for the entities is O(log(k)).