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 ledger systems and CBDCs. We present a taxonomy of privacy goals -- including anonymity, confidentiality, unlinkability, and auditability -- and map them to the cryptographic primitives, protocols, and system architectures that implement them. 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：加密货币资产与中央银行数字货币(CBDC)正在重塑分布式计算环境中价值交换的方式。这些系统融合了密码学原语、协议设计与系统架构，在提供透明性与效率的同时，也引发了隐私与合规监管方面的关键挑战。本综述对隐私保护数字支付系统进行了全面概述，涵盖去中心化账本系统与CBDC。我们提出隐私目标的分类体系——包括匿名性、机密性、不可链接性与可审计性——并将其映射至实现这些目标的密码学原语、协议与系统架构中。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。同时，我们追溯了隐私保护数字支付系统历经三代的发展演变，凸显了从基础匿名性保障向更精细的隐私-问责权衡范式的转变。最后，我们指出现存开放挑战，以激励研究者进一步探索在强隐私保护与现实可审计需求之间取得平衡的架构与解决方案。