[Resource Topic] 2022/1008: Multimodal Private Signatures

Welcome to the resource topic for 2022/1008

Title:
Multimodal Private Signatures

Authors: Khoa Nguyen, Fuchun Guo, Willy Susilo, Guomin Yang

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 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.

ePrint: https://eprint.iacr.org/2022/1008

Talk: https://www.youtube.com/watch?v=Z8KNIxnvyOE

Slides: https://iacr.org/submit/files/slides/2022/crypto/crypto2022/218/slides.pdf

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