Nicknames for Group Signatures
Guillaume Quispe, Pierre Jouvelot, Gerard Memmi
TL;DR
Nicknames for Group Signatures (NGS) presents a novel signing scheme that blends Group Signatures with Signatures with Flexible Public Keys to enable auditable anonymous transfers. The authors formalize an NGS security model, provide a concrete SEP-based construction proven secure in the ROM, and instantiate a practical blockchain prototype, NickHat, on Ethereum. Their framework supports nicknames as linked, unlinkable identities that remain verifiable as group members, with opening authorities and verifiers enabling accountable behavior while preserving user privacy. The work targets privacy-preserving, auditable transactions in finance and supply chains, offering a scalable path to real-world deployment with on-chain verification and off-chain computation. Potential future directions include stronger anonymity guarantees, threshold issuance/opening, and user revocation mechanisms to further strengthen practicality and resilience.
Abstract
Nicknames for Group Signatures (NGS) is a new signature scheme that extends Group Signatures (GS) with Signatures with Flexible Public Keys (SFPK). Via GS, each member of a group can sign messages on behalf of the group without revealing his identity, except to a designated auditor. Via SFPK, anyone can create new identities for a particular user, enabling anonymous transfers with only the intended recipient able to trace these new identities. To prevent the potential abuses that this anonymity brings, NGS integrates flexible public keys into the GS framework to support auditable transfers. In addition to introducing NGS, we describe its security model and provide a mathematical construction proved secure in the Random Oracle Model. As a practical NGS use case, we build NickHat, a blockchain-based token-exchange prototype system on top of Ethereum.