Hyperledger Fabric – Terminology

Hyperledger Fabric is private and permissioned. In order to gain access, the peers need to be enrolled through a Membership Service Provider (MSP) . It has a deterministic consensus algorithm.

Asset

An asset holds a state and has ownership. They are key / value pairs representing a value, which enables to exchange anything with monetary value. They can be tangible or intangible. They can be modified using chaincode transactions on a channel ledger i.e. the state changes of assets are recorded as transaction on the ledger.

Chaincode

Chaincode is a software that defines the asset. It also defines the transaction instruction to modify the asset. The businesses sign off on the business logic. Chaincode allow these business to interact with the ledger.

Membership Service Provider

They are sometimes also referred as Membership Identity Services. They provides IDs to the authenticated participants which can be used to define permission to the ledger.

Access Control List (ACL)

ACL is used for defining authorization on the ledger and chaincodes. They use IDs provided by MSP.

Node Types

There are two node types. They are Peer nodes and ordering nodes. Peer nodes can batch execute and verify transaction. These transactions are ordered and propagated through ordering nodes. These node types provide efficiency and scalability. A consensus protocol is defined for ordering transactions.

Ordering nodes also maintain the list of organizations that are allowed to create channels. This list of organizations is called consortium. This list is kept in the “order system channel”. This list is administered by an orderer node.Orderer also enforce access control on channels i.e. the updates to the configuration of these channels. After update the configuration block is propogated to peers.

Fabric’s Ledger

Fabric’s ledger is based on both blockchain log and current state of database. The current state can be easily queried. The log is maintained to keep asset provenance in order to provide asset creation and state changes by various members.

There is one ledger per channel and each peer maintains a copy of ledger of the channel they are a member of.

Channels

Hyperledger uses channel to provide privacy to the ledger. Only the participants of the channel have visibility to the assets and transactions on the channel. This is unlike other blockchains where all participants have access to the public ledger. So channels are restrictive message paths defining the subset of participants.

Ordering Service Implementations

In the latest version of Hyperledger fabric, there are three implementations of ordering services including Solo, Kafka and Raft.

Multitenant Fabric

A fabric can have multiple consortiums(list of organizations allowed to create channels) rendering the blockchain as multi-tenant.