Central Bank Digital Currencies: A Comprehensive CBDC Survey

What Are Central Bank Digital Currencies

Central bank digital currencies represent one of the most significant innovations in modern monetary systems. A central bank digital currency (CBDC) is a digital form of a nation’s fiat currency, issued and regulated directly by the country’s central bank. Unlike commercial bank deposits or decentralized cryptocurrencies, CBDCs carry the full backing of sovereign credit and are denominated in national currency units. As the Bank for International Settlements (BIS) defines it, a CBDC is a new form of digital money that represents a direct liability of the central bank.

The concept of CBDCs emerged from the intersection of two powerful forces: the erosion of public trust in centralized financial institutions following the 2008 financial crisis and the rapid advancement of digital payment technologies. When Bitcoin launched in 2009, it demonstrated that peer-to-peer digital transactions were possible without intermediaries. This fundamentally challenged the traditional monetary framework and prompted central banks to consider how they might digitize sovereign money while preserving monetary control. For organizations exploring how research-driven insights can transform complex documents into actionable knowledge, the Libertify interactive library offers a powerful way to engage with dense financial research.

There remains no universally accepted definition of CBDC, but scholars and institutions have converged on several core characteristics. CBDCs are electronic, universally accessible to the public (in the case of retail CBDCs), and issued by the central bank. They can be stored in digital wallets without requiring a traditional banking relationship, enabling peer-to-peer transactions in a manner similar to physical cash. Importantly, unlike stablecoins or commercial bank digital money, CBDCs are not a claim on a private institution but rather a direct obligation of the sovereign monetary authority.

Why Central Banks Are Pursuing CBDCs

The motivations driving central banks toward CBDC development are multifaceted and vary significantly across jurisdictions. A 2023 BIS survey revealed that approximately 94% of responding central banks are actively engaged in CBDC research, with 81% developing proofs of concept and around 33% having launched pilot projects. This near-universal interest reflects the convergence of several powerful economic and technological trends.

Financial inclusion stands as one of the primary drivers, particularly in developing economies where large portions of the population remain unbanked. CBDCs can provide access to digital payment infrastructure without requiring a traditional bank account, potentially reaching the estimated 1.4 billion adults worldwide who lack access to formal financial services. In countries like Nigeria and the Bahamas, CBDC programs were explicitly designed to extend financial services to underserved communities.

Monetary policy effectiveness represents another critical motivation. As cash usage declines in many advanced economies, central banks risk losing a key transmission mechanism for monetary policy. CBDCs could restore this channel by providing a digital form of central bank money that reaches the general public directly. Additionally, programmable CBDCs could enable more targeted monetary policy interventions, such as time-limited stimulus payments or conditional transfers that can only be spent in specific economic sectors.

The rise of private digital currencies and stablecoins has also accelerated CBDC development. Central banks recognize that ceding the digital payment space entirely to private actors could undermine monetary sovereignty and financial stability. The announcement of Facebook’s Libra (later Diem) project in 2019 was widely seen as a catalyst that intensified CBDC research efforts globally. Furthermore, the International Monetary Fund (IMF) has emphasized that CBDCs offer central banks an opportunity to modernize payment infrastructure while maintaining the public good nature of money.

CBDC System Architecture and Design Taxonomy

The design of a CBDC system is guided by what researchers call the CBDC Design Pyramid, a hierarchical framework that organizes the key architectural decisions that must be made when building a digital currency system. At its foundation lies the system architecture, which determines the roles and responsibilities of the central bank and commercial intermediaries in processing transactions and maintaining accounts.

The most fundamental architectural choice is between one-tier and two-tier models. In a one-tier (direct) model, the central bank manages all user accounts and processes all transactions directly. While this offers simplicity and real-time control, it places an enormous operational burden on the central bank and raises concerns about privacy, as the monetary authority would have visibility into every citizen’s financial transactions. The two-tier (indirect or hybrid) model delegates user-facing functions to licensed financial institutions while the central bank maintains oversight and controls the wholesale layer. This is by far the most commonly adopted architecture, as it leverages existing banking infrastructure while preserving monetary sovereignty.

Beyond the basic tier structure, researchers have identified more nuanced architectural classifications based on how system state is distributed and maintained. These include centralized models (where a single entity maintains all state), leaderless systems (where consensus mechanisms distribute control), macro-partitioned models (where processing is divided among entities managing separate partitions), micro-partitioned systems (where state is divided into smaller user-controlled segments), and direct models (where transactions occur between participants without third-party involvement). Each model presents distinct trade-offs among privacy, scalability, regulatory compliance, and operational complexity.

The architectural choice cascades into subsequent design decisions, including the selection of ledger technology, access models, and application domains. Understanding these interdependencies is critical for any institution or researcher evaluating CBDC implementation approaches. Studies exploring these design taxonomies can be complex; platforms like Libertify help transform such research into interactive experiences that make dense technical content more accessible.

Distributed Ledger Technology in CBDC Systems

The choice of ledger technology represents one of the most consequential technical decisions in CBDC design. Central bank digital currency systems generally employ one of three approaches: centralized ledger technology (CLT), distributed ledger technology (DLT), or a hybrid combining elements of both. Research across 26 existing CBDC projects reveals that DLT-based implementations are the most prevalent, though each approach offers distinct advantages.

Centralized ledger technology relies on a single trusted entity — typically the central bank — to manage and validate all transactions using traditional database infrastructure such as MySQL, Oracle, or SQL Server. CLT systems offer high throughput, low latency, and straightforward regulatory compliance. However, they suffer from well-documented limitations including excessive central node power, single points of failure, limited user privacy, and challenges in independent verification. Recent innovations like LedgerDB, proposed in 2020, attempt to bridge this gap by offering blockchain-like features (tamper resistance, non-repudiation, auditability) within a centralized architecture.

Distributed ledger technology distributes transaction recording and validation across multiple nodes in a network, enhancing resilience and transparency. DLT-based CBDCs can leverage both permissioned and public blockchain variants, though most central bank implementations favor permissioned networks that restrict participation to authorized entities. The choice of consensus mechanism within DLT systems — whether Practical Byzantine Fault Tolerance (PBFT), Raft, or novel protocols — significantly impacts performance, security, and energy efficiency. The European Central Bank’s digital euro research extensively evaluates both DLT and non-DLT approaches.

Hybrid CBDC systems attempt to capture the benefits of both paradigms. These implementations typically use a centralized core for high-volume transaction processing while employing DLT for specific functions such as cross-institutional settlement, audit trails, or interoperability layers. This pragmatic approach recognizes that neither pure centralization nor full distribution optimally serves all CBDC requirements simultaneously.

Digital Wallets and CBDC Access Models

The access model determines how end users interact with the CBDC system and has profound implications for privacy, security, and financial inclusion. Two primary access models have emerged: account-based and token-based approaches. In an account-based system, users are verified through identity credentials linked to accounts maintained by intermediaries or the central bank. In a token-based system, ownership is proven through possession of cryptographic tokens, similar to how physical cash ownership is established by possession.

Token-based access models have emerged as the most frequently adopted approach across existing CBDC projects. This preference reflects several advantages: token-based systems can support offline transactions, provide stronger privacy guarantees, and enable the kind of peer-to-peer transfers that make CBDCs functionally comparable to cash. However, token-based systems face challenges in anti-money laundering (AML) compliance and key management, as lost private keys could mean permanently lost funds.

Digital wallets serve as the primary interface between users and CBDC systems. Wallet design encompasses hardware wallets (physical devices storing cryptographic keys), software wallets (mobile or desktop applications), and hybrid solutions. The wallet tier in the design hierarchy must address storage security, key management, backup and recovery mechanisms, and user authentication. Several CBDC pilots have experimented with tiered wallet systems that offer different transaction limits based on the level of identity verification provided, balancing access simplicity with compliance requirements.

The integration of digital wallets into existing mobile payment ecosystems represents a critical adoption factor. In markets like China, where mobile payment platforms such as WeChat Pay and Alipay dominate, the e-CNY digital wallet has been designed to interoperate with these existing platforms while maintaining its distinct identity as central bank money. This integration strategy recognizes that user adoption depends heavily on convenience and familiarity with existing payment workflows.

Cross-Border CBDC Payments

Cross-border payments represent one of the most promising and rapidly evolving application areas for central bank digital currencies. Traditional international payment systems rely on correspondent banking networks that involve multiple intermediaries, resulting in high costs (averaging 6.3% for remittances), slow settlement times (often 2-5 business days), and limited transparency. CBDCs offer the potential to fundamentally restructure this infrastructure by enabling direct central bank-to-central bank settlement.

The most prominent cross-border CBDC initiative is Project mBridge, a collaboration between the BIS Innovation Hub and the central banks of China, Thailand, the United Arab Emirates, and Hong Kong. mBridge has demonstrated that multi-CBDC platforms can achieve near-instant cross-border settlement with significantly reduced costs. The platform uses a custom blockchain (mBridge Ledger) that connects participating central banks through a shared technical infrastructure while preserving each nation’s monetary sovereignty.

Other notable cross-border CBDC projects include Project Dunbar (involving the central banks of Australia, Malaysia, Singapore, and South Africa), Project Jura (connecting France and Switzerland), and Project Icebreaker (linking Israel, Norway, and Sweden). These experiments have revealed that interoperability between different CBDC systems is technically feasible but requires careful coordination on standards, governance, and legal frameworks. The survey of 135 research papers analyzed in recent academic literature confirms that cross-border applications are attracting growing scholarly attention, reflecting the significant economic potential of CBDC-enabled international payments.

Global CBDC Projects and Pilot Programs

The global landscape of CBDC development is remarkably diverse, with countries at various stages from initial research to full deployment. A comparative analysis of 26 existing CBDC systems reveals that while the two-tier architecture with DLT and token-based access dominates, there is no single dominant trend in application domains. Each country’s approach is shaped by its unique economic conditions, regulatory environment, and policy objectives.

China’s Digital Currency Electronic Payment (DC/EP), known as the e-CNY, represents the most advanced large-economy CBDC pilot. The program has expanded to cover dozens of cities, with hundreds of millions of digital yuan wallets opened and billions of yuan transacted. The e-CNY uses a two-tier architecture where the People’s Bank of China issues the digital currency to authorized commercial banks, which then distribute it to the public. Notably, the e-CNY supports both online and offline transactions, with hardware wallets enabling payments even without internet connectivity.

In the Caribbean, the Bahamas launched the Sand Dollar in 2020 as the world’s first fully deployed CBDC, specifically targeting financial inclusion for residents of its dispersed island geography. Jamaica followed with JAM-DEX, and Nigeria launched the eNaira, becoming the first African country to deploy a CBDC. In Europe, the European Central Bank is progressing through the investigation and preparation phases for the digital euro, with a potential launch timeline extending to 2028. India’s Reserve Bank has been piloting both wholesale and retail digital rupee variants since late 2022.

The survey findings indicate that successful CBDC deployments share several common characteristics: clear policy objectives aligned with national priorities, strong public communication and education campaigns, gradual rollout strategies that allow for iterative improvement, and robust partnerships with commercial banking sectors. Countries that have struggled with CBDC adoption, such as Nigeria with the eNaira’s initial low uptake, often faced challenges related to public trust, merchant acceptance, and competition with established mobile money platforms.

Security, Privacy, and Regulatory Challenges for CBDCs

Security and privacy represent perhaps the most complex challenge in CBDC design, requiring careful balance between competing objectives. On one hand, central banks must ensure the integrity and resilience of CBDC infrastructure against cyber threats, fraud, and operational failures. On the other hand, they must protect user privacy while maintaining the ability to enforce anti-money laundering (AML) and counter-terrorism financing (CTF) regulations.

Privacy in CBDC systems exists on a spectrum rather than as a binary choice. Full anonymity (comparable to cash) raises concerns about facilitating illicit activities, while full transparency undermines the fundamental right to financial privacy. Most CBDC designs adopt an intermediate approach, often described as “controlled anonymity” or “managed privacy,” where small-value transactions can be conducted with minimal identity disclosure while larger transactions trigger identity verification requirements.

Advanced cryptographic techniques offer promising solutions to this privacy dilemma. Zero-knowledge proofs (ZKPs) can verify transaction validity without revealing transaction details, enabling compliance checks without exposing sensitive data. Differential privacy techniques add calibrated noise to aggregated data, allowing central banks to analyze macroeconomic trends without accessing individual transaction histories. Secure multi-party computation enables collaborative analysis across institutions without sharing underlying data. These technologies are increasingly being incorporated into CBDC proof-of-concept projects.

From a regulatory perspective, CBDC deployment raises fundamental questions about the relationship between central banks, commercial banks, and citizens. The potential for deposit disintermediation — where citizens move funds from commercial bank accounts into CBDCs — could destabilize the banking sector, particularly during financial crises. Most CBDC designs address this risk through holding limits, tiered remuneration structures, or restrictions on CBDC-to-CBDC transfers. The legal frameworks governing CBDCs also vary significantly across jurisdictions, with some countries amending existing legislation while others creating entirely new regulatory categories for digital sovereign money.

Offline CBDC Payments and Financial Inclusion

Offline payment capability is a critical feature that distinguishes CBDCs from most existing digital payment methods and positions them as a genuine digital alternative to physical cash. In regions with unreliable internet connectivity — which includes significant portions of developing economies — the ability to transact without network access is essential for financial inclusion.

Offline CBDC transactions typically rely on hardware-based security elements, such as secure chips embedded in smart cards or mobile devices, that can process and validate transactions locally. These systems must address the fundamental challenge of preventing double-spending without real-time network verification. Current approaches include stored-value mechanisms with cryptographic safeguards, deferred settlement protocols that reconcile offline transactions when connectivity is restored, and tiered transaction limits that restrict offline usage to mitigate risk.

China’s e-CNY pilot has been particularly innovative in offline payment technology, demonstrating near-field communication (NFC) based transactions between hardware wallets that require no internet connection, no battery power on the receiving device, and can function with a simple “tap” gesture. Similar experiments are underway in other jurisdictions, with the Federal Reserve and several European central banks investigating offline-capable CBDC architectures.

Financial inclusion extends beyond offline capabilities to encompass the broader question of how CBDCs can serve populations that are excluded from traditional banking. Simplified onboarding processes that require minimal documentation, tiered KYC (Know Your Customer) requirements that lower barriers for basic accounts, and partnerships with non-bank entities such as mobile network operators and postal services can all contribute to broader CBDC access. The experience of mobile money platforms like M-Pesa in Kenya demonstrates that digital financial services can achieve massive adoption when designed with underserved populations in mind. Understanding how these complex research findings apply to specific organizational contexts is where interactive document platforms excel — explore the Libertify interactive library to see how.

The Future of Central Bank Digital Currencies

The trajectory of central bank digital currency development points toward several key trends that will shape the monetary landscape in the coming decade. First, interoperability across CBDC systems will become increasingly important as more countries deploy their own digital currencies. The establishment of common standards, shared governance frameworks, and technical bridges between national CBDC platforms will determine whether digital sovereign money can fulfill its potential to transform international commerce.

Programmability represents another frontier with transformative potential. Programmable CBDCs could enable automated tax collection, conditional welfare payments, smart contract integration, and new forms of monetary policy implementation. However, programmability also raises concerns about government overreach and the potential for surveillance or social control through monetary channels. The design of appropriate governance frameworks and technical safeguards will be essential to realizing the benefits of programmability while protecting civil liberties.

The convergence of CBDCs with other emerging technologies — including artificial intelligence, the Internet of Things (IoT), and decentralized finance (DeFi) — will likely create new use cases and business models not yet envisioned. Machine-to-machine payments enabled by CBDC-IoT integration, AI-driven monetary policy optimization using real-time CBDC transaction data, and hybrid CBDC-DeFi protocols that combine sovereign stability with decentralized innovation are all areas of active exploration.

Research recommendations from the comprehensive survey of 135 papers emphasize the need for continued investigation into several key areas: scalability solutions for retail CBDC systems serving billions of users, privacy-preserving technologies that satisfy both user expectations and regulatory requirements, resilient offline payment mechanisms for disaster scenarios and developing economies, and governance models for multi-national CBDC platforms. As the global financial system continues its digital transformation, CBDCs will likely play a central role in ensuring that the benefits of innovation are widely shared while the risks are carefully managed.