Crypto-assets and central bank digital currencies (CBDCs) are reshaping how value is exchanged in distributed computing environments. These systems combine cryptographic primitives, protocol design, and system architectures to provide transparency and efficiency while raising critical challenges around privacy and regulatory compliance. This survey offers a comprehensive overview of privacy-preserving digital payment systems, covering both decentralized ledgers and CBDCs. We present a taxonomy of privacy goals -- including anonymity, confidentiality, unlinkability, and auditability -- and map them to underlying cryptographic primitives, protocols, and system architectures. Our work adopts a design-oriented perspective, linking high-level privacy objectives to concrete implementations. We also trace the evolution of privacy-preserving digital payment systems through three generations, highlighting shifts from basic anonymity guarantees toward more nuanced privacy-accountability trade-offs. Finally, we identify open challenges, motivating further research into architectures and solutions that balance strong privacy with real-world auditability needs.

翻译：加密资产与中央银行数字货币（CBDCs）正在重塑分布式计算环境中的价值交换方式。这些系统融合密码学原语、协议设计与系统架构，在提供透明度与效率的同时，也引发了关于隐私与监管合规的关键挑战。本综述对隐私保护数字支付系统进行了全面概述，涵盖去中心化账本与CBDCs两大领域。我们提出了隐私目标的分类体系——包括匿名性、机密性、不可关联性与可审计性——并将其映射到底层密码学原语、协议和系统架构。本研究采用面向设计的视角，将高层隐私目标与具体实现相连接。我们还通过三代演进轨迹追溯隐私保护数字支付系统的发展历程，着重阐释其从基础匿名性保障向更精细化的隐私-问责权衡机制的转变。最后，我们指出现有挑战，以推动对兼顾强隐私保护与现实可审计性需求的架构与解决方案的进一步研究。