Paper 2022/1743

Ring Signatures with User-Controlled Linkability

Dario Fiore, IMDEA Software Institute
Lydia Garms, Keyless Technologies Limited
Dimitris Kolonelos, IMDEA Software Institute, Universidad Politecnica de Madrid
Claudio Soriente, NEC Laboratories Europe
Ida Tucker, Zondax AG

Anonymous authentication primitives, e.g., group or ring signatures, allow one to realize privacy-preserving data collection applications, as they strike a balance between authenticity of data being collected and privacy of data providers. At PKC 2021, Diaz and Lehmann defined group signatures with User-Controlled Linkability (UCL) and provided an instantiation based on BBS+ signatures. In a nutshell, a signer of a UCL group signature scheme can link any of her signatures: linking evidence can be produced at signature time, or after signatures have been output, by providing an explicit linking proof. In this paper, we introduce Ring Signatures with User-Controlled Linkability (RS-UCL). Compared to group signatures with user-controlled linkability, RS-UCL require no group manager and can be instantiated in a completely decentralized manner. We also introduce a variation, User Controlled and Autonomous Linkability (RS-UCAL), which gives the user full control of the linkability of their signatures. We provide a formal model for both RS-UCL and RS-UCAL and introduce a compiler that can upgrade any ring signature scheme to RS-UCAL. The compiler leverages a new primitive we call Anonymous Key Randomizable Signatures (AKRS) — a signature scheme where the verification key can be randomized — that can be of independent interest. We also provide different instantiations of AKRS based on Schnorr signatures and on lattices. Finally, we show that an AKRS scheme can additionally be used to construct an RS-UCL scheme.

Available format(s)
Public-key cryptography
Publication info
Published elsewhere. ESORICS 2022
ring signatures user controlled linkability privacy-enhancing pseudonyms
Contact author(s)
dario fiore @ imdea org
lydia garms @ keyless io
dimitris kolonelos @ imdea org
Claudio Soriente @ neclab eu
idatucker91 @ gmail com
2022-12-25: approved
2022-12-19: received
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      author = {Dario Fiore and Lydia Garms and Dimitris Kolonelos and Claudio Soriente and Ida Tucker},
      title = {Ring Signatures with User-Controlled Linkability},
      howpublished = {Cryptology ePrint Archive, Paper 2022/1743},
      year = {2022},
      doi = {10.1007/978-3-031-17146-8_20},
      note = {\url{}},
      url = {}
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