blockchains

Blockchains are distributed ledger technologies that record and verify transactions across a network of computers. Data is organized into blocks, each containing a batch of transactions, a timestamp, and a cryptographic hash of the previous block, creating a chronological and tamper-evident chain. The ledger is maintained by a decentralised network of nodes, which collectively validate new blocks and agree on a single version of the state without a central authority.

Transactions are validated through a consensus mechanism, such as Proof of Work or Proof of Stake. In Proof of Work, participants (miners) compete to solve a cryptographic puzzle, while Proof of Stake selects validators in proportion to their stake and other factors. Consensus mechanisms ensure that all honest participants converge on the same ledger, making retroactive tampering extremely difficult.

Blockchains can be public (permissionless) or private/consortium (permissioned). They underpin cryptocurrencies and enable programmable logic through smart contracts, allowing self-executing rules to transfer assets or enforce conditions automatically. Beyond digital currencies, blockchains are used for supply chain provenance, digital identity, decentralized finance, and tokenization of real-world assets.

Advantages often cited include tamper resistance, transparency, and censorship resistance, alongside resilience through decentralisation. Common limitations involve scalability and throughput, energy consumption in proof-of-work systems, latency for confirmation, privacy considerations, and regulatory or governance challenges. Governance is typically collaborative and open-source, with protocol upgrades that may require soft or hard forks. The concept emerged prominently with Bitcoin, introduced in 2008, and later expanded with platforms like Ethereum that support programmable smart contracts.