## 2 Related Work
### Central Bank Digital Currencies  
In addition to providing security for financial services, DLT also provides provision for secure central bank digital currencies [41]. CBDCs can be considered simply as fiat currencies issued by a central bank in place of banknotes [42; 43; 44] or complementary to cash [45], and are made available in electronic form through direct accounts with the central banks [46]. Similarly, CBDCs can be considered an electronic form of central bank money that allows for peer-to-peer transactions without the need for an intermediary [18]. In addition to serving as a means of payment, CBDCs are considered to operate as a store of value [47]. In [48], the term CBDC refers to \"a central bank granting universal, electronic, 24 \(\times\) 7, national-currency denominated and interest-bearing access to its balance sheet\". So far, only two countries (Bahamas and Jamaica) have CBDCs in operation [49]. Similar efforts are underway, where CBDC is considered as part of a new interbank settlement system or as a replacement for cash [23]. Bank of England's Digital Pound project [50], which is still in the design phase looking at the technology and policy requirements for a digital pound, is designed as a compliment to cash and focuses on the issues of privacy and offline payments. The decision to move to the build phase will be made in 2027, with a possibility of being launched by 2030 [51]. The European Central Bank has also been exploring technical solutions for a CBDC, focusing on the issues of anonymity and privacy [52; 53]. Project Rosalind [54], a collaboration between BOE and the Bank for International Settlements (BIS) is investigating how a CBDC wallet and API for a DLT-based CBDC should be designed and implemented. At the same time, central banks are researching CBDCs beyond their jurisdictions to explore their potential for cross-border payments. Notable examples are Project Icebreaker, with the participation of the central banks of Israel, Norway, and Sweden [55] and Project mBridge, which involves central banks of Hong Kong, Thailand, UAE, and China [56]. As common and standardised definitions and frameworks for CBDCs remain to be finalised, current CBDC models are specified according to two key parameters: accessibility (wholesale versus retail) and utility (retail payments versus interbank settlements). Accessibility and utility are tightly coupled because the purpose of a CBDC prescribes who has access to the currency, namely central banks, commercial banks, \"narrow banks\", non-fintech firms, and households. Wholesale CBDCs are central bank liabilities that are only accessible by banks and non-bank financial institutions. They are concerned with transactions that are processed through the Real-Time Gross Settlement (RTGS) system of a central bank, which involves interbank settlements, liquidity provision, and monetary policy implementation [57]. Retail CBDCs are central bank liabilities which are effectively identical to banknotes, and central bank deposits and can be used as an instrument for retail payments [43]. All transactions between accounts would be validated and processed by the central bank [46] or directly from payer to payee [58]. No third-party intermediaries are involved in payments; therefore, transactions are settled within a settlement platform which is independent from the RTGS system [44]. Hybrid CBDCs aim to bridge the trade-offs between wholesale and retail models by providing intermediary access to CBDCs for households and non-fintech firms. This is achieved by (i) exchange services provided by banks or \"narrow banks\" for buying and selling CBDCs in exchange for deposits [42; 59] or (ii) by fintech firms that offer financial assets which are backed by CBDCs [59]. Cross-border CBDC designs are also being investigated in efforts to overcome the intricacies of costly and slow correspondent banking chains [60].