Systematization of Knowledge: The Design Space of Digital Payment Systems with Potential for CBDC

2026-03-17

AI Summary

This study addresses the lack of a systematic understanding of the design space for digital payment systems supporting central bank digital currencies (CBDCs), particularly regarding the scalability and system integration of privacy-enhancing technologies (PETs). It presents the first large-scale, systematic review of 36 complete CBDC-oriented payment system designs, analyzing how PETs—such as zero-knowledge proofs and blind signatures—are integrated with distributed ledgers and cryptographic protocols. The work identifies common design patterns and establishes a key trade-off framework among technical requirements, revealing practical limitations of PETs in real-world deployments. Furthermore, it highlights critical research gaps, including offline payment functionality and post-quantum security, thereby offering a structured technical roadmap to guide future CBDC architecture design.

Technology Category

• Data Mining & Knowledge Management: Scalability, Parallel & Distributed Systems
• Multiagent Systems: Mechanism Design
• Game Theory and Economic Paradigms: Mechanism Design

Application Category

• Security and Privacy: Blockchains and distributed ledgers
• Economics, Online Markets and Human Computation: Economic aspects of blockchain and cryptocurrencies
• Responsible Web: Data and user privacy-enhancing technologies for the Web

Abstract

Central Bank Digital Currencies (CBDCs) are proposed as a public response to the uptake of privately run digital payments, with the digital euro, under development by the European Central Bank (ECB), serving as a prominent example. This momentum provides a unique opportunity to fundamentally rethink the future of money, and, assuming wide adoption, to establish payment systems that offer strong cryptographic security and privacy guarantees from the start. While the central banks in charge are investigating privacy-enhancing technologies (PETs), they often conclude that PETs are immature or insufficiently scalable. Moreover, these efforts tend to examine primitives in isolation, offering little insight into how a system using these PETs would scale. This systematisation of knowledge, therefore, provides a structured, top-down technical analysis of 36 payment system designs of complete system proposals that can inform CBDC designs or were explicitly proposed for this application. We identify recurring design patterns, technical trade-offs, and implementation challenges. Concluding, we highlight research gaps, including offline payments and post-quantum security.

Problem

• CBDC
• privacy-enhancing technologies
• payment systems
• scalability
• system design

Innovation

• Systematization of Knowledge
• CBDC
• Privacy-Enhancing Technologies
• Design Patterns
• Post-Quantum Security