Foundations of fully dynamic group signatures

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

Abstract

Group signatures are a central cryptographic primitive that has received a considerable amount of attention from the cryptographic community. They allow members of a group to anonymously sign on behalf of the group. Membership is overseen by a designated group manager. There is also a tracing authority that can revoke anonymity by revealing the identity of the signer if and when needed, to enforce accountability and deter abuse. For the primitive to be applicable in practice, it needs to support fully dynamic groups, i.e. users can join and leave at any time. In this work we take a close look at existing security definitions for fully dynamic group signatures. We identify a number of shortcomings in existing security definitions and fill the gap by providing a formal rigorous security model for the primitive. Our model is general and is not tailored towards 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. In the process, we identify a subtle issue inherent to one design paradigm, where new members might try to implicate older ones by means of back-dated signatures. This is not captured by existing models. We propose some inexpensive fixes for some existing constructions to avoid the issue.

• Presentation Conference Type: Conference Paper (published)
• Conference Name: Applied Cryptography and Network Security 14th International Conference, ACNS 2016
• Start Date: Jun 19, 2016
• End Date: Jun 22, 2016
• Acceptance Date: Jun 9, 2016
• Online Publication Date: Jun 9, 2016
• Publication Date: Jun 9, 2016
• Deposit Date: Mar 24, 2017
• Publicly Available Date: Mar 24, 2017
• Publisher: Springer Verlag (Germany)
• Volume: 9696
• Pages: 117-136
• Series Title: Lecture Notes in Computer Science
• Series ISSN: 0302-9743
• Book Title: Applied Cryptography and Network Security
• ISBN: 9783319395548
• DOI: https://doi.org/10.1007/978-3-319-39555-5_7
• Keywords: group signatures, security definitions
• Public URL: https://uwe-repository.worktribe.com/output/910996
• Publisher URL: http://dx.doi.org/10.1007/978-3-319-39555-5_7