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：门限签名是一种基本密码学原语，广泛应用于诸多实际场景。Boneh与Komlo（CRYPTO'22）提出的TAPS是一种兼具隐私性与问责性的门限签名方案。该方案允许合成器合并t个签名份额，同时不向公众泄露门限t或签名仲裁组信息，并指定追踪器将签名追溯至生成该签名的仲裁组。然而，TAPS存在三点不足：1）基于中心化模型构建，2）假设合成器和追踪器均诚实，3）追踪过程缺乏公证且为静态模式。本文提出一种去中心化、动态问责且私密的门限签名方案（DeTAPS），该方案实现了去中心化的合成与追踪，增强了对抗不可信合成器（追踪器）的隐私保护能力，并提供公证化动态追踪机制。具体而言，我们采用动态门限公钥加密（DTPKE）对追踪过程进行动态公证，设计非交互式零知识证明实现公证人的公开可验证性，并利用密钥聚合可搜索加密桥接TAPS和DTPKE，从而安全高效地激活公证人。此外，我们形式化定义了DeTAPS的安全性要求，提出通用构造方法并严格证明其安全性与隐私性。为评估性能，我们基于SGX2和以太坊构建了原型系统。