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Foundations of fully dynamic group signatures

Bootle, Jonathan; Cerulli, Andrea; Chaidos, Pyrros; Ghadafi, Essam; Groth, Jens


Jonathan Bootle

Andrea Cerulli

Pyrros Chaidos

Essam Ghadafi
Senior Lecturer in Computer Science

Jens Groth


Group signatures allow members of a group to anonymously sign on behalf of the group. Membership is administered by a designated group manager. The group manager can also reveal the identity of a signer if and when needed to enforce accountability and deter abuse. For group signatures to be applicable in practice, they need to support fully dynamic groups, i.e., users may join and leave at any time. Existing security definitions for fully dynamic group signatures are informal, have shortcomings, and are mutually incompatible. We fill the gap by providing a formal rigorous security model for fully dynamic group signatures. Our model is general and is not tailored toward a specific design paradigm and can therefore, as we show, be used to argue about the security of different existing constructions following different design paradigms. Our definitions are stringent and when possible incorporate protection against maliciously chosen keys. We consider both the case where the group management and tracing signatures are administered by the same authority, i.e.,a single group manager, and also the case where those roles are administered by two separate authorities, i.e., a group manager and an opening authority. We also show that a specialization of our model captures existing models for static and partially dynamic schemes. In the process, we identify a subtle gap in the security achieved by group signatures using revocation lists. We show that in such schemes new members achieve a slightly weaker notion of traceability. The flexibility of our security model allows to capture such relaxation of traceability.


Bootle, J., Cerulli, A., Chaidos, P., Ghadafi, E., & Groth, J. (2020). Foundations of fully dynamic group signatures. Journal of Cryptology, 33(4), 1822-1870.

Journal Article Type Article
Acceptance Date Jun 2, 2020
Online Publication Date Jun 2, 2020
Publication Date Oct 1, 2020
Deposit Date Apr 6, 2021
Journal Journal of Cryptology
Print ISSN 0933-2790
Electronic ISSN 1432-1378
Publisher Springer Verlag
Peer Reviewed Peer Reviewed
Volume 33
Issue 4
Pages 1822-1870
Keywords Software; Applied Mathematics; Computer Science Applications
Public URL
Publisher URL
Additional Information Received: 23 October 2018; Revised: 13 February 2020; First Online: 2 June 2020