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：门限签名是一种基础密码学原语，广泛应用于众多实际场景。由Boneh和Komlo（CRYPTO'22）提出的TAPS，是一种融合隐私性与可问责性的门限签名方案。该方案允许组合器合并t个签名份额，同时不向公众泄露门限t或签名群体信息，并授权追踪器将签名追溯至生成它的群体。然而，TAPS存在三个缺陷：1）基于中心化模型构建；2）假设组合器和追踪器均是诚实的；3）追踪过程缺乏公证且为静态特性。本文提出去中心化、门限、动态可问责且注重隐私的签名方案（DeTAPS），其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，以及经过公证的动态追踪功能。具体而言，我们采用动态门限公钥加密（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人的公开可验证性，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人。此外，我们形式化定义了DeTAPS的安全需求，提出通用构造方案，并严格证明了其安全性与隐私性。为评估性能，我们基于SGX2和以太坊构建了原型系统。