The bitcoin network is a peer-to-peer payment network that operates on a cryptographic protocol. The network requires bitcoin share difficulty structure to share transactions. An ad hoc decentralized network of volunteers is sufficient.
Messages are broadcast on a best effort basis, and nodes can leave and rejoin the network at will. Upon reconnection, a node downloads and verifies new blocks from other nodes to complete its local copy of the blockchain. An actual bitcoin transaction including the fee from a webbased cryptocurrency exchange to a hardware wallet. A bitcoin is defined by a sequence of digitally signed transactions that began with the bitcoin’s creation, as a block reward.
The owner of a bitcoin transfers it by digitally signing it over to the next owner using a bitcoin transaction, much like endorsing a traditional bank check. A payee can examine each previous transaction to verify the chain of ownership. Although it is possible to handle bitcoins individually, it would be unwieldy to require a separate transaction for every bitcoin in a transaction. Transactions are therefore allowed to contain multiple inputs and outputs, allowing bitcoins to be split and combined. This work is often called bitcoin mining. The signature is discovered rather than provided by knowledge.
Requiring a proof of work to accept a new block to the blockchain was Satoshi Nakamoto’s key innovation. The mining process involves identifying a block that, when hashed twice with SHA-256, yields a number smaller than the given difficulty target. For the bitcoin timestamp network, a valid proof of work is found by incrementing a nonce until a value is found that gives the block’s hash the required number of leading zero bits. Once the hashing has produced a valid result, the block cannot be changed without redoing the work. Majority consensus in bitcoin is represented by the longest chain, which required the greatest amount of effort to produce. If a majority of computing power is controlled by honest nodes, the honest chain will grow fastest and outpace any competing chains.