PayOff: A Regulated Central Bank Digital Currency with Private Offline Payments
Abstract
The European Union is currently preparing the legislative framework for the digital euro, a retail central bank digital currency (CBDC). The European Commission and Parliament have released regulation proposals that describe an offline payment system that offers cash-like privacy and transferability. Offline wallets will be protected by secure elements and enforce expressive policies, such as holding limits, locally. Payments will also be settled offline, meaning that users are guaranteed to retain all funds they received offline. These requirements present interesting challenges and opportunities. Prior work does not meet the desired regulatory requirements and cannot be extended easily: Designs like E-Cash do not track balances and therefore lack support for expressive policies, and existing account-based offline payment systems offer no protection if even a single secure element is compromised. Solutions with counterfeit money detection mechanisms commonly assume that counterfeit money is invalidated upon detection. Thus, offline settlement systems create opportunities for novel protocols. We propose PayOff, an account-based CBDC design for anonymous and transferable offline payments with offline settlement. PayOff offers strong user privacy and supports expressive policies such as holding limits. To increase robustness against compromised secure elements and facilitate subsequent prosecution, PayOff ensures that the central bank can identify the creators and recipients of counterfeit money. Our evaluation shows that offline payments are fast and that the central bank can handle high payment loads using moderate computing resources.
Research Area: Decentralized Systems
People
BibTex
@inproceedings{beer2026payoff,
author = {Beer, Carolin and Zingg, Sheila and Kostiainen, Kari and W{\"{u}}st, Karl and Capkun, Vedran and Capkun, Srdjan},
title = {{PayOff: A Regulated Central Bank Digital Currency with Private Offline Payments}},
booktitle = {ASIA CCS '26: Proceedings of the ACM Asia Conference on Computer and Communications Security},
address = {Bangalore, India},
year = 2026,
month = jun,
publisher = {Association for Computing Machinery},
doi = {10.1145/3779208.3805963},
url = {https://www.research-collection.ethz.ch/bitstream/handle/20.500.11850/801219/3779208.3805963.pdf}
}Research Collection: 20.500.11850/801219