Paper 2023/1070
Unlinkable Policy-Compliant Signatures for Compliant and Decentralized Anonymous Payments
Abstract
Privacy-preserving payment systems face the difficult task of balancing privacy and accountability: on one hand, users should be able to transact privately and anonymously, on the other hand, no illegal activities should be tolerated. The challenging question of finding the right balance lies at the core of the research on accountable privacy that stipulates the use of cryptographic techniques for policy enforcement. Current state-of-the-art systems are only able to enforce rather limited policies, such as spending or transaction limits, or assertions about single participants, but are unable to enforce more complex policies that for example jointly evaluate both, the private credentials of sender and recipient, such as admissible cross-border payments, let alone to do this without auditors in the loop during payment. This severely limits the cases where decentralized virtual assets can be used in accordance with regulatory compliance such as the Financial Action Task Force (FATF) travel rule, while further retaining strong privacy features.
We present unlinkable Policy-Compliant Signatures (ul-PCS), an enhanced cryptographic primitive extending the work of Badertscher et al. (TCC 21). We give rigorous definitions, formally proven constructions, and benchmarks using our prototype developed using CharmCrypto. Unlinkable PCS has the following unique combination of features:
1. It is an enhanced signature scheme where the public key encodes in a privacy-preserving way the user's verifiable credentials (obtained from a credential authority).
2. Signatures can be created (and later publicly verified) by additionally specifying a recipient's public key aside of the to-be-signed message. A valid signature can only ever be created if the attributes
Metadata
- Available format(s)
-
PDF
- Category
- Cryptographic protocols
- Publication info
- Preprint.
- Keywords
- payment systemsenhanced signatures
- Contact author(s)
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christian badertscher @ iohk io
ssedagha @ esat kuleuven be
hwaldner @ umd edu - History
- 2024-03-12: revised
- 2023-07-09: received
- See all versions
- Short URL
- https://ia.cr/2023/1070
- License
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CC BY
BibTeX
@misc{cryptoeprint:2023/1070, author = {Christian Badertscher and Mahdi Sedaghat and Hendrik Waldner}, title = {Unlinkable Policy-Compliant Signatures for Compliant and Decentralized Anonymous Payments}, howpublished = {Cryptology {ePrint} Archive, Paper 2023/1070}, year = {2023}, url = {https://eprint.iacr.org/2023/1070} }