What Is Blockchain and How Does It Work?
Blockchain is a digital record-keeping technology that allows information and transactions to be stored across a network of computers instead of relying on a single central database. It is best known as the technology behind cryptocurrencies such as Bitcoin, but its potential applications extend to areas such as supply chains, digital identity, records management and other systems.
At its core, a blockchain is a distributed digital ledger. Transactions or other records are grouped into blocks, and these blocks are connected using cryptographic techniques. This makes the recorded information tamper-evident and helps different participants maintain a shared version of the ledger.
Quick Information About Blockchain
| Feature | Details |
| Full form | Blockchain has no standard full form |
| Meaning | A distributed digital ledger |
| Main purpose | Recording and verifying digital transactions or data |
| Best-known use | Cryptocurrency |
| Data structure | Blocks linked in a chain |
| Key technology | Cryptography |
| Network | Distributed across participating computers |
| Common mechanisms | Consensus, digital signatures and hashing |
| Popular example | Bitcoin blockchain |
| Other uses | Supply chains, digital identity, records and token systems |
What Is Blockchain?
Blockchain is a system for maintaining a shared digital ledger among multiple participants. Instead of storing the entire record in one central location, copies of the ledger can be maintained across participating computers called nodes.
The records are organized into blocks. Each block is cryptographically connected to the previous block, creating a chronological chain.
According to the U.S. National Institute of Standards and Technology (NIST), blockchain is a distributed ledger in which records are grouped into blocks and cryptographically linked to earlier blocks. As additional blocks are added, older information becomes increasingly difficult to modify.
This does not mean blockchain data is absolutely impossible to change. Rather, the technology is designed to make unauthorized changes detectable and difficult under the network’s rules.
How Does Blockchain Work?
The exact process varies between blockchain networks, but a simplified blockchain transaction generally works through these steps.
- A Transaction or Record Is Created
A user first initiates a transaction or creates information that needs to be recorded.
For example, in a cryptocurrency network, one person may want to transfer digital assets to another person’s wallet.
- The Transaction Is Broadcast to the Network
The transaction is sent to participating computers on the blockchain network.
These computers, known as nodes, can check whether the transaction follows the rules of that particular blockchain.
For example, Bitcoin transactions are verified against the network’s consensus rules, and digital signatures help demonstrate that the sender is authorized to spend the relevant funds.
- Transactions Are Verified
Before a transaction becomes part of the permanent ledger, the network needs to determine whether it is valid.
Different blockchains use different consensus mechanisms to achieve agreement about which transactions should be accepted and what the next valid block should be.
Examples include:
- Proof of Work
- Proof of Stake
- Proof of Authority
- Other network-specific consensus mechanisms
Therefore, not every blockchain works through cryptocurrency mining.
- Transactions Are Grouped Into a Block
Valid transactions can be collected together into a block.
A block generally contains transaction information along with technical information that connects it to the existing blockchain.
- The Block Is Added to the Chain
After the required validation and consensus process, the new block is added to the blockchain.
Because blocks are cryptographically connected, changing information in an earlier block would affect its cryptographic relationship with subsequent blocks. This makes unauthorized alteration detectable.
- The Ledger Is Updated Across the Network
The updated blockchain information is propagated to participating nodes according to the rules of that particular network.
The result is a shared ledger that participants can use to verify the history of recorded transactions.
What Is a Block in Blockchain?
A block is a collection of records that has been added to a blockchain.
Depending on the blockchain, a block can contain information such as:
- Transactions
- A timestamp
- A reference or hash connecting it to a previous block
- A block identifier or hash
- Other technical information required by the network
The exact structure varies between blockchain systems.
What Is a Hash in Blockchain?
A hash is a cryptographic output generated from input data.
If the underlying data changes, its resulting hash also changes. Blockchain systems use cryptographic hashing for several purposes, including connecting blocks and helping detect changes to stored information.
For example, if a block contains certain transaction data and that data is modified, the cryptographic relationship involving the block can no longer match the expected values.
This is one of the reasons blockchain is considered tamper-evident.
What Are Blockchain Nodes?
A node is a computer or other system that participates in a blockchain network.
Depending on the blockchain, nodes may perform different functions, such as:
- Storing blockchain data
- Checking transactions
- Verifying blocks
- Relaying information
- Participating in consensus
In Bitcoin, for example, full nodes independently verify transactions and blocks against the network’s rules.
What Is Blockchain Decentralization?
Traditional databases can be controlled by a central organization. Blockchain networks can instead distribute record-keeping across multiple participants.
This can reduce dependence on a single central database or authority, although the degree of decentralization differs considerably between blockchain networks.
A public blockchain may allow broad participation, while a permissioned blockchain can restrict who is allowed to participate or perform certain functions.
Blockchain vs Traditional Database
| Feature | Blockchain | Traditional Database |
| Data management | Distributed in many blockchain systems | Usually controlled centrally |
| Structure | Blocks linked cryptographically | Tables, records or other structures |
| Modification | Designed to make changes detectable | Authorized users can generally edit records |
| Consensus | Often required among network participants | Usually controlled by database administrator |
| Transparency | Can be public or restricted | Usually controlled by organization |
| Main strength | Shared and tamper-evident record | Efficient centralized data management |
Blockchain is therefore not automatically better than a conventional database. Its usefulness depends on the specific problem being solved.
What Is Blockchain Used For?
Blockchain technology can be used for more than cryptocurrency.
Potential applications include:
Cryptocurrency
Bitcoin and many other cryptocurrencies use blockchain technology to maintain transaction records.
Supply Chain Management
Blockchain can potentially help organizations maintain shared records about products as they move through different stages of a supply chain.
Digital Identity
Blockchain-based systems can be designed to manage certain types of digital identity information and credentials.
Digital Records
Blockchain can be considered for applications involving records that need to be shared and independently verified among multiple organizations.
Tokenization
Blockchain networks can support digital tokens representing assets, rights or other forms of value. NIST notes that blockchain-based systems can use tokens to conduct transactions and exchange verifiable data.
Advantages of Blockchain
Some important potential advantages include:
- Distributed record-keeping: Data can be maintained across multiple participants.
- Tamper evidence: Cryptographic links make unauthorized changes easier to detect.
- Transparency: Some public blockchains allow transaction histories to be publicly viewed.
- Traceability: Records can provide a chronological history of transactions.
- Reduced dependence on intermediaries: Some blockchain systems can enable peer-to-peer transactions without a traditional central intermediary.
However, these benefits depend on how the blockchain is designed and operated.
Limitations of Blockchain
Blockchain also has limitations.
Scalability
Some blockchain networks can face limitations when transaction demand increases.
Energy Consumption
Certain consensus mechanisms, particularly Proof of Work, can require substantial computing resources.
Complexity
Blockchain systems involve cryptography, network protocols and consensus mechanisms that can make them difficult for ordinary users to understand.
Irreversible Transactions
On some blockchain networks, confirmed transactions cannot simply be reversed like a conventional bank transfer.
Security Risks
Blockchain itself can provide strong technical protections, but wallets, exchanges, smart contracts and applications built around blockchain can still have security vulnerabilities.
Is Blockchain the Same as Cryptocurrency?
No. Blockchain and cryptocurrency are not the same thing.
Blockchain is the underlying technology or record-keeping system, while cryptocurrency is one type of application that can use blockchain.
For example, Bitcoin uses a blockchain to record its transactions. However, blockchain technology can also be applied to areas that have nothing to do with cryptocurrency. NIST specifically identifies applications such as supply chains, digital identification and records management.
Frequently Asked Questions
Is blockchain secure?
Blockchain uses cryptographic techniques, distributed record-keeping and consensus mechanisms to protect the integrity of records. However, no technology is automatically secure in every situation.
Is blockchain only used for Bitcoin?
No. Bitcoin is one of the best-known applications of blockchain, but blockchain technology has many other potential uses.
Can blockchain data be changed?
Blockchain systems are generally designed to make unauthorized changes difficult and detectable. The exact ability to modify records depends on the particular blockchain and its governance rules.
What is the main purpose of blockchain?
Its main purpose is to allow participants to maintain and verify a shared digital ledger without necessarily depending on a single central record keeper.
What is the difference between blockchain and a database?
A traditional database is generally managed by a central administrator, while blockchain systems distribute record-keeping and validation across network participants. Blockchain also uses cryptographic links between blocks.
Conclusion
Blockchain is a distributed digital ledger technology that records information in linked blocks and uses cryptography and network rules to help maintain the integrity of those records. Cryptocurrency is its most famous application, but blockchain can also be used for areas such as supply chains, digital identity, tokenization and record management.
Understanding blocks, hashes, nodes, digital signatures and consensus mechanisms provides the foundation for understanding how blockchain works and why it has become an important technology in the digital economy.
