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My projects

Offline payment in CBDC & e-cash with aggregating receipt tokens

The success of CBDC (Central Bank Digital Currency) in strengthening money as a public good will depend in a large part on how it can support offline payments. Papers I have written to support success in deploying a CBDC with focus on e-cash for offline payments:

  1. A report on the IT architecture for the lage scale deployment system e-cash
  2. A proposal to implement the offline component of CBDC as e-cash
  3. Introduction to e-cash technology to realise CBDC
  4. Identifying the goals for the deployment of CBDC

Java Card

In 1994 I invented the technology that was the basis for the success of the Java Card™ platform version 2.0 and onward.

TBP

Security and cryptography

TBP

My papers

2024

  • (version 2, pre-release) How the king returns: a digital future for cash pdf

    The second revised version of this paper improves the presentation of the system architecture and provides more details on how e-cash can be smoothly integrated in the current financial system. The report introduces the Aggregating Receipt Token (ART) technology and its unique operational distinction between a payment domain that is purely offline, with payment only involving the payer and the payee, and a security domain that is intermittently online.

    A description of the functional components in the system explains many aspect of the use and implementation of e-cash with ART.

    Abstract

    This paper introduces a practical implementation of electronic cash (e-cash) at scale. The key feature presented is a secure value transfer protocol using Aggregating Receipt Tokens (ART). E-cash is a form of money with all the features of traditional cash including payer privacy, immediate settlement and no fees. Payments can be made face to face or over a distance using any form of communication, from QR codes and NFC to HTTPS. Received e-cash is stored locally for future spending as digital information in a secure device under the exclusive control of its owner. The devices work together as a large scale distributed IT system that provides society with a highly scalable, very resilient infrastructure for secure payments between citizens, corporations, banks and government agencies. The implementation of this infrastructure consists of two prime components i) an electronic purse (e-purse) as a digital bearer payment instrument to store, pay and receive e-cash and ii) an issuer as the provider of e-cash currency as a type of money integrated in a monetary system and the guarantor of its value and security. A continental-scale e-cash system that realises an offline, cash-like, digital economy, fully integrated in the existing monetary infrastructure, can be realised with the IT architecture presented here.

2023

  • Cash: The once and future king pdf linkedIn Share a link on socials.

    This paper presents the aggregating receipt token technology for e-cash as a solution for CBDC that meets all of its the key requirements for CBDC: strong protection of privacy, increased financial inclusion, protecting the availability of money as a public good and reduced costs to society of payments.

    Abstract

    It’s time to bring order to digital money through the proper issuance of Central Bank Digital Currency (CBDC). While many financial services moved to the digital realm based on centralised account ledgers, there remains an unmet need for a cash-like, distributed, digital, bearer pay- ment instrument. A hodgepodge of existing proprietary electronic cash (e-cash) products have shown this need can be met, but only in frag- mented, disconnected walled gardens. Only a central bank can be the issuer of an e-cash instrument that brings the traditional benefits of cash to the digital world. Every economy in the world will benefit when its central bank issues a digital currency. A formal model for money as a distributed information system is provided that is validated by showing cash as one of its instantiations. Guided by this model the \At\ technology is presented as an e-cash implementation that will deliver key benefits of physical cash to the digital world. It supports online and offline transactions that can be securely received with a software-only implementation. A money system based on this technology supports both monetary and security management. This aggregating receipt token e-cash solution is the only technology that meets all of the key requirements for CBDC: strong protection of privacy, increased financial inclusion,protecting the availability of money as a public good and reduced costs to society of payments.

  • Ledgers and Tokens for Central Bank Digital Currency pdf
    with Peter A. Cattaneo

    Abstract

    In this paper we illustrate the relationship between centralised ledgers and offline tokens in a complete CBDC solution that delivers fast, immediate, low-overhead payment, both on-line and off-line. We also present a technical basis for a manageable, scalable implementation that provides privacy by design and by default.

  • Transferable E-cash as central bank digital currency pdf

    Abstract

    It’s time to bring the benefits of cash to the digital world as Central Bank Digital Currency (CBDC). Many financial services have moved to the digital realm based on centralised account ledgers, leaving a still unmet need for a cash-like, distributed, digital bearer payment instrument. A hodge- podge of proprietary digital payment products have shown this need, but they only deliver cash-like payments in fragmented, disconnected walled gardens with significant limitations and fees. Only a central bank can issue an electronic cash (e-cash) payment instrument that brings all of the key benefits of cash to the digital world. When a central bank issues a digital currency, it’s citizens will see lower fees, enhanced privacy, and a root of trust that is democratically accountable.

  • Requirements for the success of a digital euro pdf

    Abstract

    The issuance of a digital currency by a central bank (CBDC) is foremost a political decision as it concerns the accessibility by the citizenry to the means of payment in a society. The technical solution to implement CBDC must follow the political objectives. This note presents the key political aspects to be considered and analyses risks, technical requirements and business perspectives of current proposals, in particular for the digital euro.

  • (version 1) How the king returns: a digital future for cash pdf

    Abstract

    Over the last 3⁄4 century society has become largely digitised. Banks were early movers digitising their ledgers as databases. Cash, banknotes and coins, up till the present could not be digitised. This paper shows how cash can be digital, as e-cash. E-cash is a form of money with all the features of traditional cash that brings additional benefits from being digital. Digital e-cash can be paid from person to person or over the Internet, it can be withdrawn from a bank account without visiting a physical ATM and deposited as easily. With the faster availability of more, fine-grained information the responsible issuing authorities can manage a digital cash system with better controls than they have today for physical cash. A formal model of money as information is presented as guide to a proper implementation of e-cash as a distributed system of secure personal digital devices, the electronic purses (e-purses), that can pay purse to purse with finality, without intermediation, protecting payer privacy and without per-transaction fees. An electronic purse is a digital bearer payment instrument. Based on this design principle and applying the aggregating token technology to secure the transfer of value, this paper demonstrates how users of the e-cash system, the issuer, financial institutions and citizens can each benefit from a suitably dedicated implementation of an e-purse to participate in the digital future of cash. With the formal model presented, the critical analysis of other types of money it affords and the elaboration of the design principle with the proper technology, this paper provides a solid foundation for the further development of a cost-effective, secure, and manageable system that delivers the digital promise of e-cash.