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.

翻译：群签名昵称方案（NGS）是一种新型签名方案，它通过灵活公钥签名（SFPK）对群签名（GS）进行了扩展。借助GS，群组成员能够代表群组对消息进行签名，同时不暴露自身身份（仅指定审计方可追溯）。通过SFPK，任何用户可为特定对象创建新身份，实现仅目标接收方可追溯新身份的匿名转账。为防止此类匿名性可能导致的滥用行为，NGS将灵活公钥集成至GS框架中以支持可审计的资产转移。除提出NGS方案外，本文还构建了其安全模型，并给出在随机预言机模型下可证明安全的数学构造。作为NGS的实际应用案例，我们在以太坊上构建了基于区块链的代币交换原型系统NickHat。