The blockchain is basically an encrypted ledger book distributed among the computer network of its users. Instead of a bank there is an algorithmic structure that encodes user identities while allowing the entire history of each bitcoin in existence to be tracked. The system’s very decentralization is what protects it from cyberattack and makes it impossible to interfere with the ledger’s contents. In order to perform a transaction, users enter two distinct sequences of randomly generated code, one public, one private. It is the safekeeping of the private key that constitutes the weakest link in the blockchain system. If the user loses access to the passkey for any reason, the assets protected by this key become irretrievable. Courtesy of Wojciech Stopiński, Cryptosteel.