Threshold signatures are a fundamental cryptographic primitive used in many practical applications. As proposed by Boneh and Komlo (CRYPTO'22), TAPS is a threshold signature that is a hybrid of privacy and accountability. It enables a combiner to combine t signature shares while revealing nothing about the threshold t or signing quorum to the public and asks a tracer to track a signature to the quorum that generates it. However, TAPS has three disadvantages: it 1) structures upon a centralized model, 2) assumes that both combiner and tracer are honest, and 3) leaves the tracing unnotarized and static. In this work, we introduce Decentralized, Threshold, dynamically Accountable and Private Signature (DeTAPS) that provides decentralized combining and tracing, enhanced privacy against untrusted combiners (tracers), and notarized and dynamic tracing. Specifically, we adopt Dynamic Threshold Public-Key Encryption (DTPKE) to dynamically notarize the tracing process, design non-interactive zero knowledge proofs to achieve public verifiability of notaries, and utilize the Key-Aggregate Searchable Encryption to bridge TAPS and DTPKE so as to awaken the notaries securely and efficiently. In addition, we formalize the definitions and security requirements for DeTAPS. Then we present a generic construction and formally prove its security and privacy. To evaluate the performance, we build a prototype based on SGX2 and Ethereum.

翻译：阈值签名是一种广泛应用于实际场景的基础密码学原语。Boneh与Komlo（CRYPTO'22）提出的TAPS方案，是一种兼具隐私性与问责性的混合阈值签名。该方案允许组合器合并t个签名份额，同时向公众隐藏阈值t或签名法定人数信息，并指定追踪器将签名追溯至生成该签名的法定人数。然而，TAPS存在三个缺陷：1）基于中心化模型构建；2）假定组合器与追踪器均为诚实角色；3）追踪过程缺乏公证且呈静态特性。本文提出去中心化、阈值化、动态问责且具有隐私性的签名方案（DeTAPS），该方案具备去中心化组合与追踪能力、针对不可信组合器（追踪器）的增强隐私保护，以及经公证的动态追踪功能。具体而言，我们采用动态阈值公钥加密（DTPKE）实现追踪过程的动态公证，设计非交互式零知识证明以达成公证的公开可验证性，并利用密钥聚合可搜索加密桥接TAPS与DTPKE，从而安全高效地激活公证功能。此外，我们形式化定义了DeTAPS的安全需求与规范，给出通用构造方案并严格证明其安全性与隐私性。性能评估方面，基于SGX2与以太坊构建了原型系统。