Multimodal private signatures

• Main Authors: NGUYEN, Khoa, GUO, Fuchun, SUSILO, Willy, YANG, Guomin
• Format: text
• Language: English
• Published: Institutional Knowledge at Singapore Management University 2022
• Subjects: new models; anonymous authentications; accountability; fine-grained information disclosure; modular constructions; zero-knowledge; lattices; pairings; Databases and Information Systems; Information Security
• Online Access: https://ink.library.smu.edu.sg/sis_research/7477; https://ink.library.smu.edu.sg/context/sis_research/article/8480/viewcontent/978_3_031_15979_4_27.pdf
• Institution: Singapore Management University

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 op about the signer’s identity id, and nothing beyond. Such partial information can flexibly be defined as op = id (as in group signatures), or as op = 0 (like in ring signatures), or more generally, as op = Gj (id), where Gj (·) is a certain disclosing function. Importantly, the value of 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.