The technology underlying the majority of cryptocurrency systems is blockchain. Blockchain is a decentralized and distributed ledger technology that records all transactions across a network of computers. It ensures security and transparency by allowing participants to verify transactions without a central authority. Each transaction is grouped into a block, which is linked to previous blocks, forming a chain. This structure enhances the integrity of data and helps prevent alterations or fraud. Blockchain is foundational to cryptocurrencies, as it also supports smart contracts and decentralized applications.