What is blockchain? A simple guide
THE SHORT ANSWER
A blockchain is a shared ledger that groups data into cryptographically linked blocks. Participants follow common rules to accept new blocks. This makes changes to past records detectable and difficult; it does not guarantee that the original data was true.
A blockchain is a shared ledger: transactions are grouped into blocks, linked together by cryptographic fingerprints.
A simple example
Alice wants to transfer a digital unit to Bob. She signs a transaction. The network checks it, and a consensus mechanism allows it to be recorded in a shared history.
How does it work?
Alice signs an instruction using her private key. Nodes can verify the signature without knowing that key.
Participants check spending rights, among other rules; the network’s mechanism determines which blocks are accepted.
Nodes synchronize their history. A confirmation does not provide the same finality guarantees on every network.
What the system provides
Participants can verify transactions using shared rules.
Cryptographic links between blocks make changes to history detectable. Resistance to rewriting depends on consensus and network security.
Some exchanges can happen without a central operator. Trust also depends on the protocol, software and how they are used.
Some possible uses
Transfer digital assets
Execute smart contract rules
Anchor a document fingerprint to check its integrity
Share a history between several organisations
A blockchain does not guarantee truthful input data or a safe project. Its usefulness depends on the problem; a conventional database is sufficient in many cases.
Key takeaway
A shared ledger, linked blocks and common validation rules. These are the foundations; each network makes different trade-offs.
Sources and further reading
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