To start a new section, hold down the apple+shift keys and click to release this object and type the section title in the box below. What is in a blockchain? Given the latest block, it is possible to access all previous Despite its apparent complexity, a blockchain is just blocks linked together in the chain, so a blockchain another type of database for recording transactions – database retains the complete history of all assets and one that is copied to all of the computers in a participating instructions executed since the very first one – making network.21 A blockchain is thus sometimes referred to as its data verifiable and independently auditable. As the a ‘distributed ledger’. Data in a blockchain is stored in number of participants grows, it becomes harder for fixed structures called ‘blocks’. The important parts of malicious actors to overcome the verification activities of a block are: the majority. Therefore the network becomes increasingly robust and secure. Indeed, blockchain solutions are being • its header, which includes metadata, such as a unique planned to protect data from the UK’s nuclear power block reference number, the time the block was created stations, flood-defence mechanisms and other critical and a link back to the previous block infrastructure.23 • its content, usually a validated list of digital assets and instruction statements, such as transactions made, their amounts and the addresses of the parties to those transactions.22 Figure 1. How the Bitcoin blockchain works Bob owes Alice To pay her, he Bob gets Alice’s The app alerts The miners verify any transactions The new block is put …hen a miner solves The algorithm …ithin ten minutes All the transactions money for lunch.needs two piecespublic key by Bitcoin ‘miners’ that Bob has occur in the network in the network so the cryptographic rewards theof Bob initiatingin the block are now He installs an appof information: scanning a  code around the world of enough bitcoins to at any time. All the that miners can problem, the winning miner with the transaction,fulfilled and Alice on his smartphone his private key and from her phone, or the impending make the payment.pending transactions verify if its discovery is †‡ bitcoins, and the he and Alice each gets paid. to create a new her public key.by having her email transaction. ‘iners’ in a given timeframe transactions are announced to the new block is added receive the first Bitcoin wallet.him the payment provide transaction are grouped inlegitimate. rest of the network.to the front ofconfirmation that A wallet app is like a address, a string of verification services.a block­ for ƒerification is the blockchain.the bitcoin was mobile banking app seemingly random verification. €ach accomplished by €ach block ˆoins signed over to her. and a wallet is like a numbers and block has a uni‚ue completing comple„ the prior block so bank account.letters.identifying number, cryptographic a chain is made – creation time and computations. the blockchain. reference to the previous block. Anyone who has a public key can send money to a Bitcoin address, but only a signature generated by the private key can release money from it. †’ Šraphic: ‹eloitte Œniversity Žress. ‘ource: American Banker Blockchain Enigma. Paradox. Opportunity 5