Trust-minimizing BDHKE-based e-cash mint using secure hardware and distributed computation

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Authors

DUFKA Antonín JANKŮ Jakub ŠVENDA Petr

Year of publication 2024
Type Article in Proceedings
Conference Proceedings of the 19th International Conference on Availability, Reliability and Security (ARES '24)
MU Faculty or unit

Faculty of Informatics

Citation
web Odkaz na autorský pre-print
Doi http://dx.doi.org/10.1145/3664476.3670889
Keywords trust-minimization; smartcards; multi-party computation; e-cash
Description The electronic cash (or e-cash) technology based on the foundational work of Chaum is emerging as a scalability and privacy layer atop of expensive and traceable blockchain-based currencies. Unlike trustless blockchains, e-cash designs inherently rely on a trusted party with full control over the currency supply. Since this trusted component cannot be eliminated from the system, we aim to minimize the trust it requires. We approach this goal from two angles. Firstly, we employ misuse-resistant hardware to mitigate the risk of compromise via physical access to the trusted device. Secondly, we divide the trusted device's capabilities among multiple independent devices, in a way that ensures unforgeability of its currency as long as at least a single device remains uncompromised. Finally, we combine both these approaches to leverage their complementary benefits. In particular, we surveyed blind protocols used in e-cash designs with the goal of identifying those suitable for misuse-resistant, yet resource-constrained devices. Based on the survey, we focused on the BDHKE-based construction suitable for the implementation on devices with limited resources. Next, we proposed a new multi-party protocol for distributing the operations needed in BDHKE-based e-cash and analyzed its security. Finally, we implemented the protocol for the JavaCard platform and demonstrated the practicality of the approach by measuring its performance on a physical smartcard.
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