International Association for Cryptologic Research

International Association
for Cryptologic Research


Paper: Multimodal Private Signatures

Khoa Nguyen , University of Wollongong
Fuchun Guo , University of Wollongong
Willy Susilo , University of Wollongong
Guomin Yang , University of Wollongong
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Presentation: Slides
Conference: CRYPTO 2022
Abstract: We introduce Multimodal Private Signature (MPS) - an anonymous signature system that offers a novel accountability feature: it allows a designated opening authority to learn \emph{some partial information}~$\ms{op}$ about the signer's identity $\ms{id}$, and nothing beyond. Such partial information can flexibly be defined as $\ms{op} = \ms{id}$ (as in group signatures), or as $\ms{op} = \mb{0}$ (like in ring signatures), or more generally, as $\ms{op} = G_j(\ms{id})$, where $G_j(\cdot)$ is certain disclosing function. Importantly, the value of $op$ is known in advanced 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.
Video from CRYPTO 2022
  title={Multimodal Private Signatures},
  author={Khoa Nguyen and Fuchun Guo and Willy Susilo and Guomin Yang},