Frequently Asked Questions ❓

Blockchain is a type of distributed ledger technology (DLT) that records data across a network of computers. Each record, or "block," contains a set of transactions and is cryptographically linked to the previous block, forming an immutable chain. This structure ensures that once data is recorded, altering it retroactively would require changing every subsequent block across every node in the network, making the system highly tamper-resistant. The technology was first described in academic research during the early 1990s and gained wider attention following its implementation as the underlying data structure for a peer-to-peer electronic payment system in 2008.

A traditional database is typically managed by a single administrator (or centralised authority) who can create, modify, and delete records freely. A blockchain, by contrast, distributes data across multiple independent nodes. Changes require consensus from the network, and the ledger is append-only, meaning records cannot be deleted or overwritten. This architecture makes blockchain more transparent and resistant to unauthorised modification, though it may process certain operations more slowly than a centralised database. Each approach has distinct strengths depending on the use case: databases excel at high-speed read/write operations, while blockchains provide stronger guarantees around data integrity and auditability.

Digital assets are broadly defined as any asset that exists in a digital form and comes with a distinct right of use. In the context of blockchain, they typically refer to cryptographically secured tokens or records on a distributed ledger. These can represent a wide range of things: units of value, access rights, certificates, loyalty points, or even digital representations of physical assets. The classification and regulatory treatment of digital assets varies significantly across jurisdictions, making it important to understand the legal framework in your country before engaging with them.

A distributed ledger is a database that is shared, replicated, and synchronised across multiple sites, institutions, or geographies. Unlike a centralised ledger controlled by one entity, a distributed ledger allows multiple participants to hold identical copies of the data. When updates occur, they are independently verified and agreed upon by the network participants through a consensus mechanism. Blockchain is one specific type of distributed ledger technology, but not all distributed ledgers use a chain-of-blocks structure. Other approaches, such as directed acyclic graphs (DAGs), also fall under the broader DLT category.

Web3 is a term used to describe a vision for a more decentralised internet, where users have greater control over their own data, digital identities, and online interactions. It encompasses technologies such as blockchain, decentralised applications (dApps), and token-based systems. While the first generation of the web (Web1) was largely read-only, and Web2 introduced interactive, user-generated content through centralised platforms, Web3 aims to reduce reliance on centralised intermediaries. The concept remains an active area of development and discussion within the technology community, and its practical implementation continues to evolve.

A consensus mechanism is the process by which nodes in a distributed network agree on the current state of the ledger. Because there is no central authority to validate transactions, the network must use an algorithm to reach agreement. The two most widely discussed approaches are Proof of Work (PoW), which requires participants to solve computationally intensive puzzles, and Proof of Stake (PoS), which selects validators based on the amount of tokens they have committed to the network. Other consensus models include Delegated Proof of Stake, Practical Byzantine Fault Tolerance (PBFT), and Proof of Authority. Each approach involves different trade-offs in terms of speed, energy consumption, and security.

A smart contract is a self-executing programme stored on a blockchain that runs automatically when predetermined conditions are met. The term was coined by computer scientist Nick Szabo in 1994. Smart contracts can automate the execution of agreements without requiring intermediaries. They are written in specialised programming languages (such as Solidity for Ethereum-based networks) and, once deployed, typically cannot be modified. This immutability is both a strength and a risk: it ensures the contract behaves predictably, but any bugs or vulnerabilities in the code become permanent. Thorough auditing and testing before deployment is therefore considered an essential practice.

Proof of Work (PoW) requires network participants, often called miners, to expend computational energy to solve cryptographic puzzles. The first to solve the puzzle earns the right to add the next block to the chain. Proof of Stake (PoS) instead selects validators based on the quantity of tokens they have locked up as collateral. PoW is generally considered more energy-intensive, while PoS is designed to be more efficient but introduces different security assumptions. Both systems aim to prevent malicious actors from manipulating the ledger, but they achieve this through fundamentally different economic incentive structures.

A node is a computer that participates in a blockchain network by maintaining a copy of the ledger and, in many cases, helping to validate and relay transactions. Full nodes store the entire transaction history and independently verify every block against the network's rules. Light nodes store only a subset of the data and rely on full nodes for verification. The more full nodes a network has, the more decentralised and resilient it generally becomes, since there is no single point of failure.

Public blockchains are open to anyone: any individual can join the network, read data, and participate in consensus. Bitcoin and Ethereum are examples. Private blockchains restrict access to a single organisation or a predefined set of participants. Permissioned (or consortium) blockchains sit in between: they are shared among several known organisations but are not open to the general public. Each type serves different needs. Public blockchains prioritise openness and censorship resistance, private blockchains offer more control and typically higher throughput, and permissioned blockchains balance transparency among trusted parties with controlled access.

A block is the fundamental unit of data in a blockchain. Each block typically contains a header and a body. The header includes metadata such as a timestamp, a reference (hash) to the previous block, a nonce (used in Proof of Work), and the Merkle root of all transactions in that block. The body contains the actual transaction data. The size and structure of blocks vary between different blockchain protocols. By including the hash of the previous block in each new header, blocks form a cryptographic chain where any alteration to an earlier block would invalidate all subsequent ones.

A decentralised application, or dApp, is a software application that runs on a peer-to-peer blockchain network rather than on a single centralised server. The backend logic of a dApp is typically implemented through smart contracts, while the frontend can be built using conventional web technologies. Because the backend runs on a distributed network, dApps can operate without a single point of control or failure. However, this architecture also introduces challenges around user experience, scalability, and the difficulty of updating code once it has been deployed to the blockchain.

A cryptographic hash function is a mathematical algorithm that takes an input of any size and produces a fixed-length output, commonly called a hash or digest. Key properties include determinism (the same input always produces the same output), pre-image resistance (it should be computationally infeasible to reverse-engineer the input from the output), and avalanche effect (a small change in the input produces a dramatically different output). In blockchain, hash functions serve multiple purposes: linking blocks together, creating unique identifiers for transactions, and forming the basis of Merkle trees used to efficiently verify data integrity.

Public-key cryptography, also known as asymmetric cryptography, uses a pair of mathematically related keys: a public key and a private key. The public key can be shared openly and is used to encrypt data or verify digital signatures, while the private key must be kept confidential and is used to decrypt data or create signatures. In blockchain systems, public-key cryptography enables users to prove ownership and authorise transactions without revealing their private key. This mechanism is fundamental to the security model of virtually all blockchain networks.

A 51% attack refers to a scenario in which a single entity or coordinated group gains control of more than half of the network's computational power (in Proof of Work systems) or staking power (in Proof of Stake systems). With majority control, the attacker could theoretically rewrite recent transaction history, prevent new transactions from being confirmed, or reverse their own transactions. In practice, executing a 51% attack on large, established networks is extremely expensive and logistically difficult. Smaller networks with fewer participants are generally more vulnerable to this type of attack.

A Merkle tree is a data structure used to efficiently summarise and verify the integrity of large sets of data. Named after computer scientist Ralph Merkle, it organises data into a tree of hash values. Each leaf node contains the hash of a data block (such as a transaction), and each parent node contains the hash of its children. The top of the tree, called the Merkle root, serves as a compact summary of all the data below it. In blockchain, Merkle trees allow nodes to verify whether a specific transaction is included in a block without downloading the entire block, which is particularly useful for lightweight clients.

In general, blockchain is designed to be append-only, meaning new data can be added but existing records cannot be modified or removed. Each block contains the cryptographic hash of the preceding block, so altering any single block would break the chain and be immediately detectable. On public blockchains, this would require controlling a majority of the network's resources, which is practically infeasible for large networks. However, it is worth noting that some private and permissioned blockchains include governance mechanisms that allow for data correction under specific, controlled circumstances, though this compromises the strict immutability principle.

In supply chain management, blockchain can provide an immutable record of a product's journey from raw materials to the end consumer. Each participant in the supply chain, including manufacturers, logistics providers, and retailers, can record their handling of goods on the shared ledger. This creates a transparent, tamper-resistant audit trail that can help verify product authenticity, track recalled items more efficiently, and reduce disputes between parties. Several organisations are piloting blockchain-based supply chain systems for food safety, pharmaceutical tracking, and luxury goods authentication.

Self-sovereign identity (SSI) is a model for managing digital identities in which the individual owns and controls their personal data, rather than relying on a centralised authority to store and verify it. Blockchain technology can support SSI by providing a decentralised infrastructure where identity credentials are issued, verified, and revoked without a single point of control. With SSI, a person could prove their age, qualifications, or address to a service provider without revealing unnecessary personal details. Several governments and international organisations are exploring SSI frameworks as a way to enhance privacy and reduce identity fraud.

In healthcare, blockchain is being explored for several purposes: secure sharing of electronic health records between providers, verifying the authenticity of pharmaceuticals through supply chain tracking, managing consent for clinical trials, and creating tamper-proof audit logs for regulatory compliance. The technology could help address longstanding challenges in healthcare data management, such as fragmented records and interoperability issues between different hospital systems. However, significant challenges remain around scalability, compliance with data protection regulations like the UK GDPR, and the need for industry-wide standards before widespread adoption is feasible.

Blockchain is being explored as a tool for increasing transparency and accountability in governance. Potential applications include tamper-resistant voting systems, public records management, land registries, and transparent grant disbursement tracking. The core idea is that by recording government actions and public decisions on a distributed ledger, citizens can independently verify that records have not been altered. Several countries and municipalities have run pilot programmes to test blockchain-based voting and public record keeping, though widespread adoption remains in early stages and faces questions around voter privacy, accessibility, and technical reliability.