Nicknames for Group Signatures

TL;DR

Nicknames for Group Signatures (NGS) is a novel cryptographic scheme that enhances group signatures with flexible, traceable identities, enabling secure, auditable anonymous transfers, and is demonstrated through a blockchain application.

Contribution

This paper introduces NGS, combining group signatures with flexible public keys, and provides a secure mathematical construction and a practical blockchain prototype.

Findings

Secure NGS scheme proven in the Random Oracle Model

Implementation of NickHat on Ethereum demonstrates practicality

Supports auditable anonymous transfers with flexible identities

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.