Blockchain
A blockchain is a distributed ledger with growing lists of records (blocks) that are securely linked together via cryptographic hashes.Each block contains a cryptographic hash of the previous block, a timestamp, and transaction data (generally represented as a Merkle tree, where data nodes are represented by leaves). Since each block contains information about the previous block, they effectively form a chain (compare linked list data structure), with each additional block linking to the ones before it. Consequently, blockchain transactions are irreversible in that, once they are recorded, the data in any given block cannot be altered retroactively without altering all subsequent blocks.
Blockchains are typically managed by a peer-to-peer (P2P) computer network for use as a public distributed ledger, where nodes collectively adhere to a consensus algorithm protocol to add and validate new transaction blocks. Although blockchain records are not unalterable, since blockchain forks are possible, blockchains may be considered secure by design and exemplify a distributed computing system with high Byzantine fault tolerance.
Features of blockchain technology
Blockchain technology has the following main features:
Decentralization
Decentralization in blockchain refers to transferring control and decision making from a centralized entity (individual, organization, or group) to a distributed network. Decentralized blockchain networks use transparency to reduce the need for trust among participants. These networks also deter participants from exerting authority or control over one another in ways that degrade the functionality of the network.
Immutability
Immutability means something cannot be changed or altered. No participant can tamper with a transaction once someone has recorded it to the shared ledger. If a transaction record includes an error, you must add a new transaction to reverse the mistake, and both transactions are visible to the network.
Consensus
A blockchain system establishes rules about participant consent for recording transactions. You can record new transactions only when the majority of participants in the network give their consent.
区块链协议
区块链协议一词是指可用于应用程序开发的不同类型的区块链平台。每种区块链协议都采用基本区块链原则来适应特定行业或应用需求。以下小节提供了一些区块链协议的示例：
Hyperledger Fabric
Hyperledger Fabric 是一个开源项目，包含一套工具和库。企业可以使用它来迅速有效地构建私有区块链应用程序。它是一种模块化通用框架，提供独特的身份管理和访问控制功能。这些功能使其非常适合各种应用，如供应链的跟踪和追踪、贸易金融、忠诚度和奖励，以及金融资产的清算结算。
以太坊 Ethereum
以太坊是一种去中心化开源区块链平台，人们可以将其用于构建公有区块链应用程序。企业以太坊 (Ethereum Enterprise) 专为企业使用案例而设计。
Corda
Corda 是一种专为企业而设计的开源区块链项目。借助 Corda，您可以构建可互操作的区块链网络，用于在严格保密的情况下进行交易。企业可以使用 Corda 的智能合约技术直接进行有价值的交易。其大部分用户是金融机构。
Quorum
Quorum 是一种源自以太坊的开源区块链协议。该协议专为在两种区块链网络中使用而设计：私有区块链网络，其中只有一个成员拥有所有节点；或者联盟区块链网络，其中包含多个成员，每个成员拥有该网络的一部分。