What is Blockchain
A blockchain is a growing list of records, called blocks, that are securely linked together utilizing cryptography. Each block includes a cryptographic hash of the previous block, a timestamp, and transaction data (typically represented as a Merkle tree, where information nodes are represented by leaves). The timestamp shows that the transaction information existed when the block was released to enter its hash. As blocks each contain information about the block previous to it, they form a chain, with each additional block enhancing the ones prior to it. Therefore, blockchains are resistant to adjustment of their data due to the fact that when taped, the data in any given block can not be modified retroactively without altering all subsequent blocks.
Blockchains are typically managed by a peer-to-peer network for use as a publicly distributed ledger, where nodes collectively adhere to a protocol to communicate and validate new blocks. Although blockchain records are not unalterable as forks are possible, blockchains may be considered secure by design and exemplify a distributed computing system with high Byzantine fault tolerance.
The blockchain was popularized by a person (or group of people) using the name Satoshi Nakamoto in 2008 to serve as the public transaction ledger of the cryptocurrency bitcoin, based on work by Stuart Haber, W. Scott Stornetta, and Dave Bayer. The identity of Satoshi Nakamoto remains unknown to date. The implementation of the blockchain within bitcoin made it the first digital currency to solve the double-spending problem without the need of a trusted authority or central server. The bitcoin design has inspired other applications and blockchains that are readable by the public and are widely used by cryptocurrencies. The blockchain is considered a type of payment rail.
What is Blockchain
Private blockchains have been proposed for business use. Computerworld called the marketing of such privatized blockchains without a proper security model “snake oil”; however, others have argued that permission blockchains, if carefully designed, maybe more decentralized and therefore more secure in practice than permissionless ones.
A blockchain is a decentralized, distributed, and oftentimes public, digital ledger consisting of records called blocks that are used to record transactions across many computers so that any involved block can not be altered retroactively, without the alteration of all subsequent blocks.
networking (node discovery, information propagation, and verification).
consensus (proof of work, proof of stake).
data (blocks, transactions).
application (smart contracts/decentralized applications, if applicable).
What is Blockchain
Blocks hold batches of valid transactions that are hashed and encoded into a Merkle tree. Each block includes the cryptographic hash of the prior block in the blockchain, linking the two. The linked blocks form a chain. This iterative process confirms the integrity of the previous block, all the way back to the initial block, known as the genesis block. To assure the integrity of a block and the data contained in it, the block is usually digitally signed.
Sometimes separate blocks can be produced concurrently, creating a temporary fork. In addition to a secure hash-based history, any blockchain has a specified algorithm for scoring different versions of the history so that one with a higher score can be selected over the others. Blocks not selected for inclusion in the chain are called orphan blocks. What is Blockchain? Peers supporting the database have different versions of the history from time to time. They keep only the highest-scoring version of the database known to them. Whenever a peer receives a higher-scoring version (usually the old version with a single new block added) they extend or overwrite their own database and retransmit the improvement to their peers. There is never an absolute guarantee that any particular entry will remain in the best version of history forever. Blockchains are typically built to add the score of new blocks onto old ones and are given incentives to extend with new ones rather than overwrite old ones. Therefore, the probability of an entry becoming superseded decreases exponentially as more blocks are built on top of it, eventually becoming very low. ch. 08 For example, bitcoin uses a proof-of-work system, where the chain with the most cumulative proof-of-work is considered the valid one by the network.