In 2009, an anonymous figure called Satoshi Nakamoto launched Bitcoin. Its underlying technology was blockchain — a distributed ledger that records transactions immutably. Each block contains a batch of transactions and a cryptographic link to the previous block. Change one block and the chain breaks.

The ledger is not stored in one place. Thousands of computers hold copies. To add a new block, they must agree on its contents. That consensus mechanism makes tampering impractical. Bitcoin uses proof of work, which burns electricity. Other networks use proof of stake, which is more efficient.

Beyond cryptocurrency

• Supply chain tracking: verify where goods came from
• Smart contracts: self-executing agreements on code
• Digital identity: tamper-proof credentials
• Land registries: secure property records

Blockchain is not a solution to everything. It is slow compared to conventional databases. It is transparent, which is not always desirable. But for records that must be trusted without a central authority, it offers something new.