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Authors:
Krenn, Stephan; Samelin, Kai; Slamanig, Daniel
Document type:
Sonstiges / Other Publication
Title:
Foundations of Dynamic Group Signatures: The Case of Malicious Openers and Issuers
Year:
2025
Language:
Englisch
Abstract:
Group signatures enable users to sign on behalf of a group while preserving anonymity, with accountability provided by a designated opener. The first rigorous model for dynamic groups (Bellare, Shi, Zhang, CT--RSA '05) captured anonymity, non-frameability, and traceability, later extended with trace-soundness (Sakai et al., PKC '12) and non-claimability (introduced as ``opening-soundness'' by Bootle et al., ACNS '16 & JoC '20). In practice, issuer and opener are often distinct entities, often implemented by different organizations and/or hardware modules. We therefore formalize and prove the consequences of a model that enforces their complete separation, allows key reuse across groups, treats issuer and opener as stateless, and makes both joining and opening non-interactive. This separation makes it necessary to reformulate traceability against a corrupt issuer and to introduce three additional unforgeability notions-key-unforgeability, certificate-unforgeability, and opening-unforgeability-for the case of a corrupt opener. Following this line of reasoning, we also develop strengthened formulations of trace-soundness and non-claimability. We prove that in this model the eight resulting properties are fully distinct: even the conjunction of any seven does not imply the eighth. This yields the first comprehensive map of group signature security in a stateless, reusable-key, and non-interactive framework, and formally demonstrates the impact of complete issuer--opener separation.
Article ID:
2025/1752
URL:
https://eprint.iacr.org/2025/1752
Department:
Fakultät für Informatik
Institute:
INF 1 - Institut für Theoretische Informatik, Mathematik und Operations Research
Chair:
Slamanig, Daniel
Research Hub UniBw M:
CODE
Open Access yes or no?:
Ja / Yes
Type of OA license:
CC BY 4.0
Licence URL:
https://creativecommons.org/licenses/by/4.0/deed.de
Miscellaneous:
Preprint auf IACR Cryptology ePrint Archiv
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