Hyperledger Fabric

Hyperledger Fabric

Hyperledger Fabric is a platform for deploying blockchain networks. 

The ledger, smart contracts, and consensus between members are maintained by using Fabric protocols. 

Fabric is designed for business use cases where the blockchain is operated by a set of known, identified, and often vetted participants. This capability is known as a permissioned blockchain. 

A permissioned blockchain provides a way to secure the interactions among a group of entities that know each other, have common business interests, and want to manage a decentralized network (rather than turning management of their ledgers over to a single party). By relying on the identities of the peers, a permissioned blockchain can use traditional crash fault tolerant (CFT) or Byzantine fault tolerant (BFT) consensus protocols that are used by many other distributed programs.

Hyperledger Fabric offers high levels of performance, protection, and transaction privacy. Fabric is the leader in blockchain for business, and can enable modular components to suit various use cases. 

The IBM Blockchain Platform is built upon Hyperledger Fabric and, as a result, a basic understanding of Fabric's components and architecture is important for developers and decision makers to understand.

Fabric consists of the following basic components: 

 A ledger on Fabric consists of the world state and the blockchain. The world state contains the status of all assets that are tracked on the ledger (who owns a particular asset, for example), while the blockchain contains a history of all state changes. Ledgers are replicated across a channel (more on channels below) and stored on peers. 

Peers are the transaction endpoints for organizations and make up much of the physical structure of a network. They are maintained by members (organizations) whose identities are known by the blockchain network. Peers can maintain multiple ledgers (they have one for every channel they are a member of) and endorse transactions. 

A channel contains a subset of network members who want to communicate and transact privately. Ledgers are channel specific (that is, every channel has a separate ledger). Only the peers on a channel can see the assets and transactions for its ledger. As a result, channels ensure privacy for participants within the network. 

Hyperledger Fabric smart contracts are implemented in chaincode. When an application needs to interact with the ledger, it invokes these contracts by sending transactions into the Fabric network. This is the case because chaincode predominately interacts only with the database component of the ledger and not the historical transaction log. 

The Ordering Service, usually composed of multiple orderers, provides consensus and ordering of transaction. It does so by bundling transactions into blocks, which are then added to the blockchain.

The certificate authority (CA) identifies all entities in the network: Peers, the ordering service, and the participants who are submitting transactions and accessing the ledger. These identities are provided and secured by using a public key infrastructure (PKI). Peers use the CA to cryptographically sign transactions and contracts, whereas participants use the CA to prove that they have a right to access the network. 

The Hyperledger Fabric Client SDKs enable interaction between your client application and your blockchain network. With support for multiple languages, the SDK contains APIs that allow an app to connect to and to access the smart contracts and the ledger for the channel the peer is on.