%% Last Updated: - [[2021-02-16]] tags: [#kleur/rood] %% A blockchain is a distributed ledger that is cryptographically secured. ## Key features of a blockchain ### Distributed The blockchain builds on already existing theories and practices around [[Distributed computing]]. Each blockchain node is like a server. The fundamental difference is that distributed computing typically utilizes identically configured infrastructure, whereas blockchains have built-in resilience to differences between computers. Since many blockchains are public, a blockchain must be able to function regardless of operating systems and configurations. ### Immutable A ledger is a chronological record of events. Blockchains work similarly in that blocks can always be added to the end of the blockchain, but previous blocks, once accepted, are immutable. Immutability is essential to a blockchain because it allows the propagation of what would otherwise have been a single source of truth. Its immutability is safeguarded by cryptographic security. ## [[Cryptography|Cryptographically secure]] ## Problems any blockchain has to solve ### Synchronicity and [[Consensus]] Data in blockchains are received asynchronously by the nodes, but blockchains must be able to process this input and collectively come to a consensus about the current state of the blockchain. Without a solution to this problem, the blockchain becomes forked. ## Blockchain applications ## Blockchains in practice ## See also - [[Blockchain Scalability and its Foundations in Distributed Systems]] - [[Principle of Atomicity]]