Master Thesis
Secure and Privacy-preserving CBDC Offline Payments using a Secure Element
Central-Bank Digital Currency (CBDC) is a form of central bank money, on par with cash and central-bank reserves. Retail CBDCs are available to the general public for retail payments and aim at empowering individuals to conduct digital payments irrespective of their location or the quality of their network coverage. Achieving this goal requires support for secure offline payments. Offline payments assume a setting where the payers and the payees are offline, except when they withdraw or deposit their CBDCs. For this reason, they are also essential for resilient and robust digital payments that can operate even in the events of blackouts or power outages.
A recent proposal [1] combines secure elements with the identification of double spenders to achieve a high level of security. The secure element ensures that double spending attacks are expensive and cannot be executed at scale, while the identification of double spenders ensures that, in the event that such an attack succeeds, responsible parties will be identified and held accountable.
The Digital Euro project of the European Central Bank [2] also foresees the use of secure elements for this CBDC.
The goal of this thesis is to analyze how secure elements and cryptographic tools are combined to solve the problem stated above, with a focus on the security of the resulting scheme. In particular, the student will explore how changes in some trust assumptions affect the security properties satisfied by the scheme.
References
[2] European Central Bank: Digital Euro. 2021-2026