Cryptology ePrint Archive: Report 2006/454

How to Win the Clone Wars: \\ Efficient Periodic n-Times Anonymous Authentication

Jan Camenisch and Susan Hohenberger and Markulf Kohlweiss and Anna Lysyanskaya and Mira Meyerovich

Abstract: We create a credential system that lets a user anonymously authenticate at most $n$ times in a single time period. A user withdraws a dispenser of $n$ e-tokens. She shows an e-token to a verifier to authenticate herself; each e-token can be used only once, however, the dispenser automatically refreshes every time period. The only prior solution to this problem, due to Damg{\aa}rd et al.~[DDP05], uses protocols that are a factor of $k$ slower for the user and verifier, where $k$ is the security parameter. Damg{\aa}rd et al. also only support one authentication per time period, while we support $n$. Because our construction is based on e-cash, we can use existing techniques to identify a cheating user, trace all of her e-tokens, and revoke her dispensers. We also offer a new anonymity service: glitch protection for basically honest users who (occasionally) reuse e-tokens. The verifier can always recognize a reused e-token; however, we preserve the anonymity of users who do not reuse e-tokens too often.

Category / Keywords: cryptographic protocols / electronic commerce and payment, e-cash

Publication Info: Full version of an extended abstract published in Proceedings of ACM CCS 2006, ACM Press.

Date: received 30 Nov 2006, last revised 11 Apr 2007

Contact author: mira at cs brown edu

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Version: 20070412:012739 (All versions of this report)

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