What is blockchain?

What is Blockchain?

Blockchain is a shared ledger, allowing thousands of connected computers or servers to maintain a single, secured and immutable ledger

Gary Woodfine

Gary Woodfine

15 May 2024

A fundamental component of Cryptocurrency is a technology referred to as Blockchain. In fact, without Blockchain technology most probably wouldn't be cryptocurrency projects, because it is the underlying technology that is implemented through various channels to make it all work.

The Bitcoin: A Peer-to-Peer Electronic Cash System introduced the term chain of blocks, which later would evolve into Blockchain later to evolve into “blockchain”, where a chronologically ordered sequence of blocks containing transactions is produced by the protocol.

A blockchain is a linked list of transactions stored on a network of computers.

This is probably the simplest definition of what a blockchain is, however it also obfuscates a lot of the technical complexity. The fundamental concept behind Blockchain is that it is a technology that enables the secure sharing of data, thus a Blockchain is a type of database.

Attributes of blockchain

Blockchain Technology is the backbone of cryptocurrency which makes use of cryptography to keep the data secure.

Blockchain is a shared ledger, more commonly referred to as a ledger, allowing thousands of connected computers or servers to maintain a single, secured and immutable ledger enabling the execution of user transactions without involving any third party intermediaries.

The top three attributes of blockchains are:

  1. Decentralisation - Transactions are executed on a network of computers
  2. Immutable - Transactions cannot be changed once committed
  3. Transparent - Transactions can be viewed by anyone.

What is a ledger

A ledger is a record of financial transactions. In accounting, it is the principal book of accounts. It is a book in which all ledger accounts and related monetary transactions are maintained in a summarised and classified form. All accounts combined make ledger and form a permanent record of all transactions.

A crypto public ledger is a record-keeping system. The ledger maintains the identities of participants anonymously, their cryptocurrency balances, and a record of all the transactions executed between network participants.

How blockchains work

A blockchain is made up of blocks which contain data of transactions. When a transaction is created over a blockchain network, a new block will be created, representing the new transaction. This new block is broadcast over the peer-to-peer network, consisting of computers, known as nodes, which then validate the transaction. A verified transaction can involve cryptocurrency, contracts, records, or any other valuable information.

A blockchain is a data structure of blocks that are chained together to form a collection of records, called a ledger, with cryptography being a key ingredient in the process.

Once a transaction is verified, it is combined with other blocks to create a new block of data for the ledger. For each new transaction, a secured block is created, which is secured and bound to each other using cryptographic principles. Whenever a new block is created, it is added to the existing Blockchain network confirming that it is secured and immutable.

Each block contains :

  1. A list of transactions
  2. A hash for the block
  3. The previous blocks hash

Data within each block is what is called its hash value which is generated by passing some data through a formula, and the result produced by the formula is called a hash. Usually, the hash is a string of characters, and hashes generated by a specific formula are always the same length, regardless of how much data you feed into it.

The hash serves as the unique digital fingerprint for each block. Along with a hash value, a checksum is also produced for a specific piece of data, and it verifies the authenticity of the data.

Hash function

A hash function is a mathematical function with the following properties:

  • An input of anything, i.e. string, number, floating number
  • Produces a fixed size output as 128-bit hash outcome or even a 256-bit outcome
  • Collission resistant
  • Hides data within it

The diagram below provides an illustration of how hash function can be used to generate a unique value for any input that is provided to it. The outcome of the hash function is also known as the digest hash sum .

A blockchain doesn't have a storage mechanism; it has a set of protocols that govern the way in which information is forged.

We discuss how Blockchain technology uses cryptography in more detail because cryptography because as you explore more about blockchain technology you find that it makes heavy use of cryptography throughout.

Benefits of Blockchain

A blockchain is a distributed ledger, similar to a database, but rather than being controlled by a central authority the ledger is dispersed across multiple computers, which can be located all over the world and run by anyone with an Internet connection.

a blockchain is a ledger through which data is added and updated in real-time via consensus of the different nodes running the software in the network. An important note to add here is, that once the data is added to the ledger, it cannot be removed or edited like with a typical database.


It impossible to change the data or altering the data in a block; the data present inside the Blockchain is permanent and cannot be deleted or undone.


utilising blockchain technology, organisations and enterprises can go for a complete decentralised network where there is no need for any centralised authority, thus improving the transparency of the entire system.

High Availability

Blockchain is a decentralised system of P2P (Peer To Peer) network which is highly available due to its decentralised nature. All nodes are computer on a P2P network, therefore, even if one peer goes down, the other peers still work.

High Security

all the transactions of Blockchain are cryptographic-ally secure and provide integrity. Thus instead of relying on third-party, you need to put your trust in cryptographic algorithms.

Consensus Mechanisms

A core component of blockchain is what is referred to as a consensus mechanism. This primarily due to the fact that in a blockchain network there is no central entity, and all peers in the network are equal to each other and serve as validators of the state of the ledger.

A consensus mechanism is a system that Blockchain's use to validate the authenticity of transactions and maintain security. This system ensures that all legitimate transactions are recorded on the blockchain and that each copy of the blockchain contains all valid transactions.

A consensus mechanism enables the processing transactions without middlemen.

Consensus mechanisms are the protocols, algorithms, or other computer systems that allow cryptocurrencies to work. They are systems of agreement that determine the validity of transactions and governance of the blockchain.

  • Proof-of-Work: Miners compete against each other to validate the next transaction block and earn a reward. This is a highly energy-intensive consensus mechanism but brings a high degree of trust.
  • Proof-of-stake (PoS): A consensus mechanism wherein those with the largest holding of the networks currency validate new blocks. This enables faster and lower-cost transactions. It rewards those with the biggest stake in the network for continued participation.
  • Proof-of-Authority: Proof-of-authority is not as common but has a unique form. It is used mainly by private companies or organisations that use blocks created by vetted sources who have special permissions to access the network. Assurances are based on reputation and authority rather than public consensus as with other mechanisms.
  • Delegated Proof-of-Stake: Delegated proof-of-stake is a variation of PoS in which users who stake their coins can vote on the number of delegates to create new blocks.
  • Proof-of-Capacity: Proof-of-capacity currencies rely on a computers available hard drive storage space for a decentralised block verification and generation process.
  • Proof-of-Activity: The proof-of-activity consensus mechanism is a hybrid of proof-of-stake and proof-of-work in which the miner seeks to utilise the best of both systems.
  • Proof-of-Elapsed Time: Proof-of-elapsed time uses a random timer that operates independently at every node to randomly assign the block verification to a miner.
  • Proof-of-Burn: With proof-of-burn, consensus is driven by miners periodically burning coins, a process of permanently deleting or eliminating that specific coin from circulation. This validates new transactions while preventing inflation.

Through a series of clever Game Theory incentives, cryptography, and distributed consensus, a blockchain can achieve secure and accurate consensus on the state of the ledger, just like a central clearinghouse, but over a decentralised network where no single entity is in control.

Use cases for blockchain

There are 3 distinct ideal use cases for blockchain technology

  1. Data traceability and transparency
  2. secure transfer of assets
  3. Decentralised applications

Data traceability and transparency

A common requirement in industries is to ensure there is 100% transparent traceability of their manufacturing methods or products in their supply chain. Primarily to mitigate the risk fraud or adhere to stringent compliance and regulatory requirements. Blockchain data repositories provide a solution, when coupled with IoT to significantly improve the reliability of information collection.

Industry sectors where this may typically be implemented

  • Maritime and logistics for international trade - reduce fraud and delivery errors.
  • Health & Medical care - ensure a decentralised storage of medical records to provide patients control over their own medical records.
  • Pharmaceutical - Combat the proliferation of dangerous, counterfeit medicines.
  • Food processing - ensure improved monitoring of food provenance, storage, and transport conditions.
  • Certification of documents - identity, birth certificates, diplomas, voter registration
  • automotive, aeronautical, railways - trace the supply chain and record the history of devices.

Secure Transfer of Assets

The transfer of assets is not necessarily limited to financial assets, such as securities (shares, bonds), pension funds or mutual funds. Its applications, therefore, go far beyond the financial and insurance sectors. The blockchain architecture offers unparalleled security for sensitive transactions, which can involve the exchange of securities and movable or immovable property.

cryptocurrency used within the blockchain is a token, more commonly referred to as Coin, with the value of an exchange currency. Tokenization enables the acquisition of a security or property shared between several parties. It consists of applying the model of dilution of the capital of a company to any object.

The Tokenization process provides the advantage of enabling the raising of funds from individuals, thus avoiding having to take out a bank loan to make a property investment. By tokenising a house, an owner acquires only a part of it and does not enjoy 100% of its possible rental income, but he avoids a constraining and very expensive bank loan.

Decentralised applications

Blockchain technology is predominantly used in the deployment of smart contracts and Decentralised Applications (DApps). The use of smart contracts enables the storage of records and to automate actions via autonomous programs.

DApps provide

  • Reduction of costs associated with the presence of intermediary actors within a transaction process while defining a new model of governance considered fairer and more ethical.
  • Secure transactions by means of a contract established based on strict conditions: if these conditions are not met, the program does not run.
  • Improving the transparency of networks by making information 100% accessible.

Features of Blockchain

  • Secure - Impossible to hack or tamper with transactions
  • Global - Adopted worldwide
  • Automated operations - Operations are fully automated through software.
  • Open Source - Blockchain is an open source technology
  • Distributed - Blockchain works in a distributed mode, in which records are stored in all nodes in the network.

The differences between blockchains and databases

A blockchain is a read- and append-only storage methodology. This means that blocks can only be created and read in the blockchain ledger. Blocks in a blockchain cannot be updated or deleted; blocks can only be appended to the end of a blockchain. There is no access control in a public blockchain as it is open for both read and write operations. & Delete_ (CRUD) operation model. Each database has an administrator when it is created, and they will assign access control to the other users. Relational databases are mostly maintained by a single central authority in control of all the application data.

Blockchain technology was designed for decentralized applications and no single central authority controls the data.

Blockchain inherently provides immutability, security & redundancy (ISR), whereas traditional databases need additional investment to provide ISR for the data they hold. One of the main advantages of blockchain-based solutions over databases is that little to no investment is required in the management of infrastructure.

Blockchain and Digital Money

There have been many attempts to create digital money, but they had always failed.

The prevailing issue is trust. If someone creates a new currency, how can we trust that they won't manipulate the currency to their favour.

Bitcoin was designed to solve this problem by using a blockchain because nobody controls the blockchain; it's run by the people who use it. What's more, bitcoins can't be faked, hacked or double spent, so people that own this money can trust that it has some value.

Bitcoin is the first decentralised digital currency, which has changed the way we compute things and the way we operate software and computers.

Bitcoin provides the following properties:

  • International network of payments
  • uses cryptography to control and management instead of a central authority
  • Completely digital
  • Controlled and limited supply


blockchains are a protocol architecture that removes the need to trust individuals in a permission-less network, fostering social scalability, and a medium of value transfer free from the control or corruption of malicious parties.

In a blockchain network, storage and data are redundant, meaning that as long as people run node, there is no central point of failure. As a result, they have achieved significant attention and hype for a variety of use cases

Gary Woodfine
Gary Woodfine

Back-end software engineer

Experienced software developer, specialising in API Development, API Design API Strategy and Web Application Development. Helping companies thrive in the API economy by offering a range of consultancy services, training and mentoring.

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