{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,5,9]],"date-time":"2026-05-09T18:34:34Z","timestamp":1778351674807,"version":"3.51.4"},"reference-count":64,"publisher":"MDPI AG","issue":"5","license":[{"start":{"date-parts":[[2021,5,14]],"date-time":"2021-05-14T00:00:00Z","timestamp":1620950400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Horizon 2020","award":["H2020-ICT-2018-2 825215"],"award-info":[{"award-number":["H2020-ICT-2018-2 825215"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Future Internet"],"abstract":"<jats:p>In recent years, electronic retail payment mechanisms, especially e-commerce and card payments at the point of sale, have increasingly replaced cash in many developed countries. As a result, societies are losing a critical public retail payment option, and retail consumers are losing important rights associated with using cash. To address this concern, we propose an approach to digital currency that would allow people without banking relationships to transact electronically and privately, including both e-commerce purchases and point-of-sale purchases that are required to be cashless. Our proposal introduces a government-backed, privately-operated digital currency infrastructure to ensure that every transaction is registered by a bank or money services business, and it relies upon non-custodial wallets backed by privacy-enhancing technology, such as blind signatures or zero-knowledge proofs, to ensure that transaction counterparties are not revealed. Our approach to digital currency can also facilitate more efficient and transparent clearing, settlement, and management of systemic risk. We argue that our system can restore and preserve the salient features of cash, including privacy, owner-custodianship, fungibility, and accessibility, while also preserving fractional reserve banking and the existing two-tiered banking system. We also show that it is possible to introduce regulation of digital currency transactions involving non-custodial wallets that unconditionally protect the privacy of end-users.<\/jats:p>","DOI":"10.3390\/fi13050130","type":"journal-article","created":{"date-parts":[[2021,5,14]],"date-time":"2021-05-14T10:54:22Z","timestamp":1620989662000},"page":"130","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":26,"title":["A Digital Currency Architecture for Privacy and Owner-Custodianship"],"prefix":"10.3390","volume":"13","author":[{"given":"Geoffrey","family":"Goodell","sequence":"first","affiliation":[{"name":"Centre for Blockchain Technologies, University College London, London DA13, UK"}]},{"given":"Hazem Danny","family":"Al-Nakib","sequence":"additional","affiliation":[{"name":"Centre for Blockchain Technologies, University College London, London DA13, UK"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-5460-5940","authenticated-orcid":false,"given":"Paolo","family":"Tasca","sequence":"additional","affiliation":[{"name":"Centre for Blockchain Technologies, University College London, London DA13, UK"}]}],"member":"1968","published-online":{"date-parts":[[2021,5,14]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","unstructured":"Mancini-Griffoli, T., Peria, M., Agur, I., Ari, A., Kiff, J., Popescu, A., and Rochon, C. (2020, May 10). Casting Light on Central Bank Digital Currency. IMF Staff Discusion Note SDN\/18\/08. Available online: https:\/\/www.imf.org\/~\/media\/Files\/Publications\/SDN\/2018\/SDN1808.ashx.","DOI":"10.5089\/9781484384572.006"},{"key":"ref_2","unstructured":"Auer, R., Cornelli, G., and Frost, J. (2020, April 04). BIS Bulletin 3. Available online: https:\/\/www.bis.org\/publ\/bisbull03.pdf."},{"key":"ref_3","unstructured":"Goodell, G. (2021, January 08). Comment on FR Doc #2020-28437. Public Submission to the US Financial Crimes Enforcement Network, Available online: https:\/\/downloads.regulations.gov\/FINCEN-2020-0020-4720\/attachment_1.pdf."},{"key":"ref_4","unstructured":"(2021, January 07). Access to Cash Review (UK), Final Report. Available online: https:\/\/www.accesstocash.org.uk\/media\/1087\/final-report-final-web.pdf."},{"key":"ref_5","unstructured":"Sadeghi, M. (2021, January 07). Fact Check: No US Law Requires Businesses to Take Cash, But Local Laws May Mandate It, USA Today, Available online: https:\/\/eu.usatoday.com\/story\/news\/factcheck\/2020\/09\/16\/fact-check-cashless-businesses-banned-only-some-local-state-laws\/3330804001\/."},{"key":"ref_6","unstructured":"Tisher, D., Evans, J., Cross, K., Scott, R., and Oxley, I. (2020). Where to Withdraw? Mapping Access to Cash across the UK, University of Bristol. Available online: http:\/\/www.bristol.ac.uk\/media-library\/sites\/geography\/pfrc\/Where%20to%20withdraw%20-%20mapping%20access%20to%20cash%20across%20the%20UK.pdf."},{"key":"ref_7","unstructured":"Armer, P. (1968). Privacy Aspects of the Cashless and Checkless Society. Testimony before the US Senate Subcommittee on Administrative Practice and Procedure, RAND Corporation. Available online: https:\/\/www.rand.org\/content\/dam\/rand\/pubs\/papers\/2013\/P3822.pdf."},{"key":"ref_8","first-page":"8","article-title":"Computer Technology and Surveillance","volume":"24","author":"Armer","year":"1975","journal-title":"Comput. People"},{"key":"ref_9","doi-asserted-by":"crossref","unstructured":"Nissenbaum, H. (2020, September 29). Deregulating Collection: Must Privacy Give Way to Use Regulation?. Available online: https:\/\/doi.org\/10.2139\/ssrn.3092282.","DOI":"10.2139\/ssrn.3092282"},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"22","DOI":"10.24908\/ss.v19i1.13986","article-title":"Data management for platform-mediated public services: Challenges and best practices","volume":"19","author":"Rychwalska","year":"2021","journal-title":"Surveill. Soc."},{"key":"ref_11","unstructured":"Goodell, G. (2020, June 10). Privacy by Design in Value-Exchange Systems. Discussion Paper. Available online: https:\/\/arxiv.org\/abs\/2006.05892."},{"key":"ref_12","doi-asserted-by":"crossref","unstructured":"Goodell, G., and Aste, T. (2019). Can Cryptocurrencies Preserve Privacy and Comply with Regulations?. Front. Blockchain.","DOI":"10.3389\/fbloc.2019.00004"},{"key":"ref_13","unstructured":"Mersch, Y. (2020, May 11). Speech at the Consensus 2020 Virtual Conference. Available online: https:\/\/www.ecb.europa.eu\/press\/key\/date\/2020\/html\/ecb.sp200511~01209cb324.en.html."},{"key":"ref_14","unstructured":"Zhang, T. (2020). Keynote Address on Central Bank Digital Currency, London School of Economics. Available online: https:\/\/www.imf.org\/en\/News\/Articles\/2020\/03\/19\/sp031920-deputy-managing-director-tao-zhangs-keynote-address-on-central-bank-digital-currency."},{"key":"ref_15","unstructured":"Monetary Authority of Singapore, Bank of Canada, and Bank of England (2020, April 30). Cross-Border Interbank Payments and Settlements: Emerging Opportunities for Digital Transformation, Available online: https:\/\/www.mas.gov.sg\/-\/media\/MAS\/ProjectUbin\/Cross-Border-Interbank-Payments-and-Settlements.pdf."},{"key":"ref_16","unstructured":"Bank of England (2020, March 16). Central Bank Digital Currency: Opportunities, Challenges and Design. Discussion Paper. Available online: https:\/\/www.bankofengland.co.uk\/paper\/2020\/central-bank-digital-currency-opportunities-challenges-and-design-discussion-paper."},{"key":"ref_17","unstructured":"Nakamoto, S. (2018, October 04). Bitcoin: A Peer-to-Peer Electronic Cash System. Available online: https:\/\/bitcoin.org\/bitcoin.pdf."},{"key":"ref_18","unstructured":"Buterin, V. (2021, January 08). Ethereum Whitepaper. Available online: https:\/\/ethereum.org\/en\/whitepaper\/."},{"key":"ref_19","doi-asserted-by":"crossref","unstructured":"Keister, T., and Sanches, D. (2019). Should Central Banks Issue Digital Currency? Federal Reserve Bank of Philadelphia Working Papers WP 19-26, Available online: https:\/\/ideas.repec.org\/p\/fip\/fedpwp\/19-26.html.","DOI":"10.21799\/frbp.wp.2019.26"},{"key":"ref_20","unstructured":"International Organization for Standardization (ISO) (2020). Blockchain and Distributed Ledger Technologies\u2014Vocabulary, ISO. [1st ed.]. Available online: https:\/\/www.iso.org\/obp\/ui\/#iso:std:iso:22739:ed-1:v1:en."},{"key":"ref_21","unstructured":"Chaum, D., Grothoff, C., and Moser, T. (2021, February 25). How to Issue a Central Bank Digital Currency. Swiss National Bank Working Paper 3\/2021. Available online: https:\/\/www.snb.ch\/n\/mmr\/reference\/working_paper_2021_03\/source\/working_paper_2021_03.n.pdf."},{"key":"ref_22","unstructured":"Calle, G., and Eidan, D. (2020, May 05). Central Bank Digital Currency: An Innovation in Payments. R3 White Paper. Available online: https:\/\/www.r3.com\/reports\/central-bank-digital-currency-an-innovation-in-payments\/."},{"key":"ref_23","unstructured":"dGen (2020, May 05). CBDC: Considerations for the Digital Euro. Available online: https:\/\/www.dgen.org\/cbdc."},{"key":"ref_24","doi-asserted-by":"crossref","unstructured":"Agur, I., Ari, A., and Dell\u2019Ariccia, G. (2020, May 05). How Could Central Bank Digital Currencies be Designed? SUERF Policy Note Issue 129. Available online: https:\/\/www.suerf.org\/policynotes\/9763\/how-could-central-bank-digital-currencies-be-designed.","DOI":"10.2139\/ssrn.3523125"},{"key":"ref_25","unstructured":"Lagarde, C. (2020, February 26). Winds of Change: The Case for New Digital Currency. Speech to Singapore Fintech Festival as Prepared for Delivery. Available online: https:\/\/www.imf.org\/en\/News\/Articles\/2018\/11\/13\/sp111418-winds-of-change-the-case-for-new-digital-currency."},{"key":"ref_26","doi-asserted-by":"crossref","unstructured":"Agur, I., Ari, A., and Dell\u2019Ariccia, G. (2020, April 27). Designing Central Bank Digital Currencies. IMF Working Paper. Available online: https:\/\/www.imf.org\/-\/media\/Files\/Publications\/WP\/2019\/wpiea2019252-print-pdf.ashx.","DOI":"10.5089\/9781513519883.001"},{"key":"ref_27","unstructured":"Benaloh, J. (2020, December 11). What if Responsible Encryption Back-Doors Were Possible?, Lawfare Blog, Available online: https:\/\/www.lawfareblog.com\/what-if-responsible-encryption-back-doors-were-possible."},{"key":"ref_28","doi-asserted-by":"crossref","unstructured":"Courtois, N., and Mercer, R. (2017, January 19\u201321). Stealth Address and Key Management Techniques in Blockchain Systems. Proceedings of the 3rd International Conference on Information Systems Security and Privacy (ICISSP 2017), Porto, Portugal. Available online: http:\/\/www.scitepress.org\/Papers\/2017\/62700\/62700.pdf.","DOI":"10.5220\/0006270005590566"},{"key":"ref_29","unstructured":"International Organization for Standardization (ISO) (2020). Blockchain and Distributed Ledger Technologies\u2014 Privacy and Personally Identifiable Information Protection Considerations, ISO. [1st ed.]. ISO\/TR 23244:2020."},{"key":"ref_30","unstructured":"Pedersen, T. (1991, January 11\u201315). Non-Interactive and Information-Theoretic Secure Verifiable Secret Sharing. Proceedings of the Advances in Cryptology (CRYPTO \u201991), Santa Barbara, CA, USA. Available online: https:\/\/link.springer.com\/content\/pdf\/10.1007%2F3-540-46766-1_9.pdf."},{"key":"ref_31","unstructured":"van Wirdum, A. (2018, October 10). Confidential Transactions: How Hiding Transaction Amounts Increases Bitcoin Privacy, Bitcoin Magazine, Available online: https:\/\/bitcoinmagazine.com\/articles\/confidential-transactions-how-hiding-transaction-amounts-increases-bitcoin-privacy-1464892525\/."},{"key":"ref_32","unstructured":"Rivest, R., Shamir, A., and Tauman, Y. (2018). How to Leak a Secret, Springer. Available online: https:\/\/link.springer.com\/content\/pdf\/10.1007%2F3-540-45682-1_32.pdf."},{"key":"ref_33","unstructured":"Ben-Sasson, E., Bentov, I., Horesh, Y., and Riabzev, M. (2018). Scalable, Transparent, and Post-Quantum Secure Computational Integrity, International Association for Cryptologic Research (IACR). Available online: https:\/\/eprint.iacr.org\/2018\/046.pdf."},{"key":"ref_34","unstructured":"Guan, Z., Wan, Z., Yang, Y., Zhou, Y., and Huang, B. (2019). BlockMaze: An Efficient Privacy-Preserving Account-Model Blockchain Based on zk-SNARKs, International Association for Cryptologic Research (IACR). Available online: https:\/\/eprint.iacr.org\/2019\/1354."},{"key":"ref_35","unstructured":"Zcash (2020, April 15). Sapling. Available online: https:\/\/z.cash\/upgrade\/sapling\/."},{"key":"ref_36","doi-asserted-by":"crossref","unstructured":"Stam, M. (2013). Sub-linear Blind Ring Signatures without Random Oracles. Cryptography and Coding, Springer. IMACC 2013. Lecture Notes in Computer Science.","DOI":"10.1007\/978-3-642-45239-0"},{"key":"ref_37","unstructured":"Zimmermann, P. (1991). Why I Wrote PGP. PGP User\u2019s Guide, Massachusetts Institute of Technology. Available online: https:\/\/www.philzimmermann.com\/EN\/essays\/WhyIWrotePGP.html."},{"key":"ref_38","unstructured":"Wong, J., and Kar, I. (2020, July 16). Everything You Need to Know about the Ethereum \u2018Hard Fork\u2019, Quartz, Available online: https:\/\/qz.com\/730004\/everything-you-need-to-know-about-the-ethereum-hard-fork\/."},{"key":"ref_39","unstructured":"Software in the Public Interest, Inc (2020, July 16). Debian Security FAQ. Available online: https:\/\/www.debian.org\/security\/faq."},{"key":"ref_40","unstructured":"U.S. Securities and Exchange Commission (2020, July 16). SEC Proposes Improvements to Governance of Market Data Plans. Press Release, Available online: https:\/\/www.sec.gov\/news\/press-release\/2020-5."},{"key":"ref_41","unstructured":"United States Securities and Exchange Commission Division of Trading and Markets (2020, November 03). Memorandum to SEC Market Structure Advisory Committee, Available online: http:\/\/sec.gov\/spotlight\/emsac\/memo-rule-611-regulation-nms.pdf."},{"key":"ref_42","unstructured":"Bank for International Settlements (2020, May 31). Payment, Clearing and Settlement Systems in the CPSS Countries. Committee on Payment and Settlement Systems \u201cRed Book\u201d, Volume 2. Available online: https:\/\/www.bis.org\/cpmi\/publ\/d105.pdf."},{"key":"ref_43","unstructured":"Bank for International Settlements (2020, April 16). Payment, Clearing and Settlement Systems in the United Kingdom. Committee on Payment and Settlement Systems \u201cRed Book\u201d. Available online: https:\/\/www.bis.org\/cpmi\/publ\/d105_uk.pdf."},{"key":"ref_44","first-page":"69","article-title":"Keys under doormats: Mandating insecurity by requiring government access to all data and communications","volume":"1","author":"Abelson","year":"2015","journal-title":"J. Cybersecur."},{"key":"ref_45","doi-asserted-by":"crossref","unstructured":"Bordo, M.D., and Levin, A.T. (2017). Central Bank Digital Currency and the Future of Monetary Policy, National Bureau of Economic Research.","DOI":"10.3386\/w23711"},{"key":"ref_46","unstructured":"Castro, M., and Liskov, B. (1999, January 22\u201325). Practical Byzantine Fault Tolerance. Proceedings of the Third Symposium on Operating Systems Design and Implementation, New Orleans, LA, USA. Available online: http:\/\/pmg.csail.mit.edu\/papers\/osdi99.pdf."},{"key":"ref_47","unstructured":"Ripple (2020, March 03). XRP. Available online: https:\/\/ripple.com\/xrp\/."},{"key":"ref_48","unstructured":"Visa (2020, March 03). Fact Sheet. Available online: https:\/\/usa.visa.com\/dam\/VCOM\/download\/corporate\/media\/visanet-technology\/aboutvisafactsheet.pdf."},{"key":"ref_49","unstructured":"Visa (2020, March 03). Visa Acceptance for Retailers. Available online: https:\/\/web.archive.org\/web\/20200103093557\/https:\/\/usa.visa.com\/run-your-business\/small-business-tools\/retail.html."},{"key":"ref_50","unstructured":"Bindseil, U. (2020, May 21). Tiered CBDC and the Financial System. European Central Bank Working Paper Series 2351. Available online: https:\/\/www.ecb.europa.eu\/pub\/pdf\/scpwps\/ecb.wp2351~c8c18bbd60.en.pdf."},{"key":"ref_51","doi-asserted-by":"crossref","first-page":"679","DOI":"10.1109\/TDSC.2019.2910058","article-title":"Traceable Monero: Anonymous Cryptocurrency with Enhanced Accountability","volume":"18","author":"Li","year":"2021","journal-title":"IEEE Trans. Dependable Secur. Comput."},{"key":"ref_52","unstructured":"Abelson, H., Anderson, R., Bellovin, S., Benaloh, J., Blaze, M., Diffie, W., Gilmore, J., Neumann, P., Rivest, R., and Schiller, J. (2019, March 11). The Risks of Key Recovery, Key Escrow, and Trusted Third-Party Encryption. Available online: https:\/\/academiccommons.columbia.edu\/doi\/10.7916\/D8R2176H\/download."},{"key":"ref_53","unstructured":"(2019, March 11). 115th Congress of the United States. H.R. 5823, \u201cSecure Data Act of 2018.\u201d, introduced by Representative Zoe Lofgren [D-CA-19], Available online: https:\/\/www.congress.gov\/bill\/115th-congress\/house-bill\/5823."},{"key":"ref_54","unstructured":"Thomson, I. (2019, March 11). French say \u2018Non, merci\u2019 to Encryption Backdoors, The Register, Available online: https:\/\/www.theregister.co.uk\/2016\/01\/15\/france_backdoor_law\/."},{"key":"ref_55","unstructured":"Financial Action Task Force (FATF) (2018, September 16). The FATF Recommendations. Updated February 2018. Available online: http:\/\/www.fatf-gafi.org\/media\/fatf\/documents\/recommendations\/pdfs\/FATF%20Recommendations%202012.pdf."},{"key":"ref_56","doi-asserted-by":"crossref","unstructured":"Goodell, G., and Aste, T. (2019). A Decentralised Digital Identity Architecture. Front. Blockchain.","DOI":"10.2139\/ssrn.3342238"},{"key":"ref_57","unstructured":"Pilkington, M. (2020, May 11). Blockchain Technology: Principles and Applications. Working Paper. Available online: https:\/\/papers.ssrn.com\/sol3\/papers.cfm?abstract_id=2662660."},{"key":"ref_58","unstructured":"Siliski, M., and Pott, A. (2019, October 24). Blockchain Alternatives: The Right Tool for the Job, Medium, Available online: https:\/\/medium.com\/swlh\/blockchain-alternatives-b21184ccc345."},{"key":"ref_59","doi-asserted-by":"crossref","unstructured":"Tasca, P., and Morini, M. (Harvard Business Review China, 2017). Managing Risk Under the Blockchain Paradigm, Harvard Business Review China.","DOI":"10.1007\/978-3-319-98911-2_9"},{"key":"ref_60","doi-asserted-by":"crossref","unstructured":"Fern\u00e1ndez-Villaverde, J., Sanches, D., Schilling, L., and Uhlig, H. (2020). Central Bank Digital Currency: Central Banking for All?, Federal Reserve Bank of Philadelphia. Working Paper WP 20-19.","DOI":"10.21799\/frbp.wp.2020.19"},{"key":"ref_61","unstructured":"Sveriges Riksbank (2020, May 25). Technical Solution for the e-Krona Pilot. Available online: https:\/\/www.riksbank.se\/en-gb\/payments\u2013cash\/e-krona\/technical-solution-for-the-e-krona-pilot\/."},{"key":"ref_62","unstructured":"Adrian, T., and Mancini-Griffoli, T. (2020, May 21). The Rise of Digital Money. International Monetary Fund FinTech Note 19\/01. Available online: https:\/\/www.imf.org\/~\/media\/Files\/Publications\/FTN063\/2019\/English\/FTNEA2019001.ashx."},{"key":"ref_63","unstructured":"Bouchaud, M., Lyons, T., Olive, M.S., and Timsit, K. (2020, July 26). Central Banks and the Future of Digital Money. Available online: https:\/\/pages.consensys.net\/central-banks-and-the-future-of-digital-money."},{"key":"ref_64","unstructured":"Auer, R., and B\u00f6hme, R. (2020). The technology of retail central bank digital currency. BIS Q. Rev., 85\u2013100. Available online: https:\/\/www.bis.org\/publ\/qtrpdf\/r_qt2003j.pdf."}],"container-title":["Future Internet"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1999-5903\/13\/5\/130\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T06:00:47Z","timestamp":1760162447000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1999-5903\/13\/5\/130"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2021,5,14]]},"references-count":64,"journal-issue":{"issue":"5","published-online":{"date-parts":[[2021,5]]}},"alternative-id":["fi13050130"],"URL":"https:\/\/doi.org\/10.3390\/fi13050130","relation":{},"ISSN":["1999-5903"],"issn-type":[{"value":"1999-5903","type":"electronic"}],"subject":[],"published":{"date-parts":[[2021,5,14]]}}}