Minutes of the CBDC Technology Forum - February 2024

Minutes

Date of meeting: 8 February 2024

Item 1: Welcome

Tom Mutton (Chair) welcomed Members to the tenth meeting of the CBDC Technology Forum.

The Chair noted the agenda for the meeting would comprise presentations from two of the four subgroups that have been temporarily established to help explore the design options for the digital pound architecture. The Chair then invited members of Subgroups 2 and 3 to present the progress of their work to date.

Item 2: Subgroup 2’s presentation

Members of Subgroup 2, tasked with exploring the models of interaction between PIPs, presented their findings. They explored three models of interaction between PIPs then defined use cases to assess against those models. The following models of interaction were explored:

• Model one was a centralised model in which PIPs could interact with each other through the core digital pound system operated by the Bank of England (the Bank).
• Model two was a centralised model where PIPs could interact with each other through a third-party operator. This third-party operator could also facilitate PIPs’ interactions with the core systems operated by the Bank.
• Model three was a decentralised model in which PIPs could interact with each other directly.

They explored a range of use cases, from basic payment initiation to interoperability with different forms of money. They also made some preliminary assumptions to guide their assessment of the use cases, such as assuming the digital pound would be account based and that PIPs would be responsible for strong customer authentication.

They noted that their research did not reveal significant differences among the three models in terms of complexity of transactions, processing steps and the number of calls between parties, but further work would be needed to assess this practically. They explained, however, that model three would provide additional privacy assurances since all non-core data could pass directly between PIPs without reference to a third party or the Bank.

They explained that a key difference between the centralised approach of models one and two, and the decentralised approach of model three, was that the former could support standardisation across the network. The decentralised approach, however, would rely on PIPs to enforce standards.

Members of Subgroup 2 also presented their preliminary assessment on messaging standards. They explained that whereas ISO20022 standard provided a useful taxonomy and data dictionary, there were no specific ISO messages that, in their opinion, would be perfect for the digital pound. They highlighted complexities around ISO22002 noting that, since it was Extensible Markup Language (XML) based, it would be challenging to implement for the digital pound application programming interfaces (APIs). Their emerging thinking indicated that there were likely no messaging standards that could be adopted without modification for the digital pound.

They noted that a key area for their future exploration was key management and determining which parties should sign different messages and which parties would be able to check those signatures. They also expected to explore how the different models of interactions could operate in parallel and how a token-based assumption would affect their use cases.

Item 3: Subgroup 3’s presentation

Members of Subgroup 3, tasked with exploring core ledger technologies for the digital pound, presented their findings. They stated that their goals were to help identify options for core ledger technology and how those options would meet the requirements related to transaction speed, privacy and uptime that were set out in the Bank’s Technology Working Paper. They considered both centralised and decentralised governance. They also considered distributed architectures.^{footnote [1]}

They explained that distributed ledger technology (DLT) models that achieve high consistency and trust but do not currently have high transaction speeds. Therefore, some members of Subgroup 3 suggested that layer 2 solutions would likely be needed to meet performance requirements. But centralised solutions might face similar performance constraints when trying to achieve high consistency.

They also presented their assessment on some centralised database systems and DLTs based on the maximum settlement rate and availability. They noted some technical requirements, such as achieving 30,000 transactions per second, favoured a centralised approach, but they did not have a final view on requirements such as availability. They reasoned that their assessment might vary based on functionality and use cases.

Members of Subgroup 3 asked the Bank whether they would use an off-the-shelf ledger solution for the digital pound. The Bank noted that this would be assessed further.

Members of Subgroup 3 also wondered whether the core ledger would need to achieve 100% consistency. The Bank explained that consistency would be critical for confidence a digital pound.

Members of Subgroup 3 expected to explore ledger technology solutions in-depth and compare different options.

Item 4: Closing remarks

The Chair closed the meeting and thanked Members for contributions.

Attendees

Bank of England

Tom Mutton (Chair)

Danny Russell

Members

Adrian Field, OneID

Alain Martin, Thales

Andrew Flatt, Archax

Ashley Lannquist, IMF

Bejoy Das Gupta, eCurrency

David MacKeith, AWS

Edwin Aoki, Paypal

Gary King, Lloyds

Georgios Samakovitis, University of Greenwich

Joshua Jeeson Daniel, JP Morgan

Julia Demidova, FIS

Keith Bear, Cambridge Centre for Alternative Finance

Kene Ezeji-Okoye, Millicent Labs

Lars Hupel, Giesecke+Devrient

Lauren Del Giudice, Idemia

Lee Braine, Barclays

Mark Shaw, Spotify

Paul Lucas, IBM

Tim Moncrieff, Visa

Vikram Kimyani, Oracle

Will Drewry, Google

Observers

National Cyber Security Centre

Apologies

Alan Ainsworth, Open Banking

Dominic Black, Ledgerz

Inga Mullins, Fluency

Geoff Goodell, UCL

James Whittle, Pay.UK

Michael Adams, Quali-Sign

Paul Carey, Stripe

Richard Brown, R3

Sarah Meiklejohn, IC3

Simon Brayshaw, Motorway

Tom Beresford, Starling