blockchainA blockchain—the technology underlying bitcoinBitcoin is a digital currency (also called crypto-currency) ... and other cryptocurrencies—is a shared digital ledger, or a continually updated list of all transactions. This decentralized ledger keeps a record of each transaction that occurs across a fully distributed or peer-to- peer network, either public or private. A blockchain’s integrity hinges on strong cryptography that validates and chains together blocks of transactions, making it nearly impossible to tamper with any individual transaction record without being detected.