Anonymous Identification in Ad Hoc Groups

Yevgeniy Dodis, Aggelos Kiayias, Antonio Nicolosi, Victor Shoup

Research output: Chapter in Book/Report/Conference proceedingConference contribution


We introduce Ad hoc Anonymous Identification schemes, a new multi-user cryptographic primitive that allows participants from a user population to form ad-hoc groups, and then prove membership anonymously in such groups. Our schemes are based on the notion of accumulator with one-way domain, a natural extension of cryptographic accumulators we introduce in this work. We provide a formal model for Ad hoc Anonymous Identification schemes and design secure such schemes both generically (based on any accumulator with one-way domain) and for a specific efficient implementation of such an accumulator based on the Strong RSA Assumption. A salient feature of our approach is that all the identification protocols take time independent of the size of the ad-hoc group. All our schemes and notions can be generally and efficiently amended so that they allow the recovery of the signer’s identity by an authority, if the latter is desired.

Using the Fiat-Shamir transform, we also obtain constant-size, signer-ambiguous group and ring signatures (provably secure in the Random Oracle Model). For ring signatures, this is the first such constant-size scheme, as all the previous proposals had signature size proportional to the size of the ring. For group signatures, we obtain schemes comparable in performance with state-of-the-art schemes, with the additional feature that the role of the group manager during key registration is extremely simple and essentially passive: all it does is accept the public key of the new member (and update the constant-size public key of the group).
Original languageEnglish
Title of host publicationAdvances in Cryptology - EUROCRYPT 2004
Subtitle of host publicationInternational Conference on the Theory and Applications of Cryptographic Techniques, Interlaken, Switzerland, May 2-6, 2004. Proceedings
EditorsChristian Cachin, Jan L. Camenisch
Place of PublicationBerlin, Heidelberg
PublisherSpringer Berlin Heidelberg
Number of pages18
ISBN (Electronic)978-3-540-24676-3
ISBN (Print)978-3-540-21935-4
Publication statusPublished - 2004

Publication series

NameLecture Notes in Computer Science
PublisherSpringer Berlin Heidelberg
ISSN (Print)0302-9743

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