# From Bitcoin to Central Bank Digital Currencies: Making Sense of the Digital Money Revolution
## 3 Experiments, Proofs-of-Concept, and Pilots
Regarding the infrastructure, we have an equal number of experiments exploring DLT and conventional databases (10 each), six looking into both \begin{table}
\begin{tabular}{c c c} \hline \hline
**Characteristic** & **Alternatives** & **Description** \\ \hline \multirow{3}{*}{Application Area [43; 51]} & Wholesale & The currency is intended only for financial institutions which hold accounts in the central bank \\ \cline{2-3}  & Retail & The currency is intended for use by the general public \\ \hline \multirow{6}{*}{Architecture [56] —related to Operating Model [69], Access Model [68]} & Direct CBDC & CDBC is a claim on the central bank; onboarding is performed by either central bank or intermediaries (respecting KYC regulations); all payments handled by central bank \\ \cline{2-3}  & Indirect/Synthetic CBDC & CBDC is a claim on an intermediary, onboarding is performed by intermediaries (respecting KYC regulations); retail payments are handled by intermediaries, wholesale payments handled by the central bank \\ \cline{2-3}  & & CDBC is a claim on the central bank; onboarding is performed by intermediaries (respecting KYC regulations); retail payments are handled by intermediaries, but the central bank periodically records all retail balances and operates a backup technical infrastructure allowing it to restart the payment system if intermediaries fail \\ \cline{2-3}  & Intermediated CBDC & Like Hybrid CDBC, but the central bank maintains only a wholesale ledger, rather than all transactions \\ \hline \multirow{3}{*}{Access Technology [67]} & Account-based access & The value is linked to an account, with ownership tied to identity; no privacy by default \\ \cline{2-3}  & Token-based access & The value is linked to demonstrated knowledge, like a digital signature, eventually stored in a hardware device; provides privacy by default \\ \hline \multirow{6}{*}{Central Bank Infrastructure [67]} & Conventional & The transactions are stored in a logically centralized ledger; the actual storage may be distributed, but the control over the information is centralized \\ \cline{2-3}  & Distributed ledger technologies (DLT)-based & The transactions are stored in a logically distributed ledger; the control over information must be harmonized with a consensus mechanism; may make use of Blockchain technology (like R3 Corda or Quorum) \\ \hline \multirow{3}{*}{Interlinkages [67]} & National & Access is reserved to residents of a particular monetary \\ \cline{2-3}  & International & Accessible to non-residents, allowing for cross-border retail payments; this is allowed by default if the access is token-based \\ \cline{2-3}  & Centralized & Only the central bank can verify and commit transactions \\ \cline{2-3}  & Partially Decentralized & The central bank provides tokens to selected financial institutions to either safeguard or act as intermediaries \\ \cline{2-3}  & Decentralized & The ledger is run on a DLT, allowing for decentralized transaction verification and commit \\ \hline \multirow{3}{*}{Availability and Limitations [69] and Restrictions on Access [68]} & Unlimited usage & While theoretically possible, it may conflict with particular central bank goals due to effects on the banking sector, monetary policy, and financial stability \\ \cline{2-3}  & Geographical limits & Only accessible to current residents of a monetary area \\ \cline{2-3}  & Value limits & Maximum limits on the amount that can be stored in a particular account or instrument \\ \hline \hline \end{tabular}
\end{table} 
Table 2: CDBC main characteristics/design goals; Source: authors’ own. and six without information. An equal number of experiments explore account-based and token-based (11 each) for access technology, with seven exploring both and five not providing information. Finally, the overall majority of experiments is limited to national interlinkages (14), with only five exploring international interoperation and one undefined on this characteristic.