Paper 2022/1008

Multimodal Private Signatures

Khoa Nguyen, University of Wollongong
Fuchun Guo, University of Wollongong
Willy Susilo, University of Wollongong
Guomin Yang, University of Wollongong

We introduce Multimodal Private Signature (MPS) - an anonymous signature system that offers a novel accountability feature: it allows a designated opening authority to learn some partial information $\mathsf{op}$ about the signer's identity $\mathsf{id}$, and nothing beyond. Such partial information can flexibly be defined as $\mathsf{op} = \mathsf{id}$ (as in group signatures), or as $\mathsf{op} = \mathbf{0}$ (like in ring signatures), or more generally, as $\mathsf{op} = G_j(\mathsf{id})$, where $G_j(\cdot)$ is a certain disclosing function. Importantly, the value of $\mathsf{op}$ is known in advance by the signer, and hence, the latter can decide whether she/he wants to disclose that piece of information. The concept of MPS significantly generalizes the notion of tracing in traditional anonymity-oriented signature primitives, and can enable various new and appealing privacy-preserving applications. We formalize the definitions and security requirements for MPS. We next present a generic construction to demonstrate the feasibility of designing MPS in a modular manner and from commonly used cryptographic building blocks (ordinary signatures, public-key encryption and NIZKs). We also provide an efficient construction in the standard model based on pairings, and a lattice-based construction in the random oracle model.

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Publication info
Published by the IACR in CRYPTO 2022
new models anonymity accountability fine-grained information disclosure zero-knowledge lattices pairings
Contact author(s)
khoa @ uow edu au
fuchun @ uow edu au
wsusilo @ uow edu au
gmyang @ smu edu sg
2022-08-07: approved
2022-08-05: received
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      author = {Khoa Nguyen and Fuchun Guo and Willy Susilo and Guomin Yang},
      title = {Multimodal Private Signatures},
      howpublished = {Cryptology ePrint Archive, Paper 2022/1008},
      year = {2022},
      note = {\url{}},
      url = {}
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