Hyperledger Fabric Transaction Flow

Hyperledger Fabric Transaction Flow

• Transaction proposal is sent to endorsing peers
• Endorsing peers respond to the transaction proposal
• Invocation request is sent to the ordering services
• Invocation response is sent to the peers, updating the ledger and committing transactions
• The ledger is updated

Transaction Flow Assumptions in Hyperledger

• A properly set up channel is necessary
• Application users must register and enroll with the organization's Certificate Authority (CA)
• The CA provides a cryptographic key for user authentication
• Chaincode contains transaction instructions and an agreed-upon price for assets
• The endorsement policy dictates that all peers must endorse transactions

Transaction Flow Breakdown

• A transaction proposal is initiated by sending a request to endorsing peers
• Endorsing peers respond with their endorsement or rejection of the proposal
• An invocation request is then sent to the ordering services to arrange the transaction
• The ordering service sends an invocation response to the peers, initiating the ledger update
• The ledger is updated to reflect the committed transaction

Transaction Proposal Details

• Clients use an SDK or an application to initiate the transaction
• The transaction proposal is prepared and sent to endorsing peers for evaluation
• The proposal invokes a chaincode function for reading from or writing to the peer ledger

Endorsement Response Details

• Endorsing peers validate the transaction proposal by checking the format, duplicates, and signatures
• Signature verification involves using the MSP and client authorization to validate the authenticity of the request
• Endorsing peers pass transaction proposal inputs to their chaincode function
• The chaincode produces a response value and read/write set by referencing its database
• The outcome along with the endorsing peer's signature is sent back to the SDK, this constitutes the "proposal response"

Ordering Services Details

• The SDK application validates the endorsing peer signatures and compares endorsement responses for consistency and agreement
• The application broadcasts the transaction with the transaction proposal and endorsement responses
• The transaction contains read/write sets, endorsing peer signatures, and the channel ID
• The ordering service receives transactions from all channels, chronologically orders them, and creates transaction blocks

Invocation Response Details

• The invocation response sends blocks of transactions to all peers in the channel
• Transactions are validated to check whether they meet the endorsement policy
• Verification ensures that changes to the ledger state correspond with the execution
• Transactions are tagged as valid or invalid based on the validation results

Ledger Update Details

• All peers append the block to the channel chain
• Valid transactions is written to the current state database
• An event is emitted that an invocation response has been immutably appended to the chain
• This also reports the validation status of whether the transaction was validated or invalidated

Chaincode Details

• Chaincode handles the business logic of the Hyperledger blockchain
• Chaincode functions similarly to Ethereum smart contracts, providing functions for blockchain network interaction
• Chaincode functions include creating assets/tokens, executing calculations, managing data on the blockchain, and setting permissions
• Chaincodes require a proposal to be invoked, such as updating/querying the ledger
• Chaincode must be installed on channel peers
• Multiple chaincodes can be deployed, each with different endorsement policies coded

Chaincode Technology Details

• Chaincodes can be written in Go, Java, and Node JS
• Chain codes are deployed using Docker containers
• Docker container ensures that the code stays environment free ensuring no OS dependency
• Chaincodes reside in isolated Docker containers for endorsing peer process isolation

Chaincode Lifecycle

• Developing Chaincode: The first step in the process
• You can carry out this in a language that Fabric supports, such as Go, JavaScript, or Java
• Packaging Chaincode: Once the chaincode is developed, it then gets packaged into a chaincode package
• The Chaincode package contains chaincode binaries and metadata
• Installing Chaincode on Peers designates it for the peers
• Approving Chaincode Definition, each organization must approve a smart contract definition to fit their organization
• Committing Definition to Channel happens after a number of organizations have approved the chaincode definitions
• Invoking Chaincode involves submitting transaction proposals for endorsement, collecting endorsements, and then submitting the endorsed transaction to the ordering service
• To Upgrade Chaincode you must follow a similar process to the initial deployment but with a new version

Hyperledger Fabric Certificate Authority and Membership Service Provider

• Hyperledger Fabric certificate authority is a tool for generating certificates
• Certificates are generated by specifying the username, password and affiliations
• A new user connecting to blockchain networks must be granted a certificate from an issuing authority, a part of MSP
• This certificate generation acts as enrollment in the Hyperledger System
• CA functionalities involves:
  • Issuance of Enrollment Certificates
  • Certificate renewal and revocation
  • Registration of identities, or connects to LDAP as the user registry

Fabric CA Architecture

• Fabric CA follows a server-client architecture
• Fabric-CA root server is the root node of the entire tree
• Types to Fabric CA Server interaction:
  • Fabric-CA client
  • or Fabric SDK
• HA Proxy Server:
  • Balances traffic to CA server cluster
  • CA-servers in the cluster share a common database
  • MySQL/PostgreSQL and LDAP is common for identities and certs

CA (Certificate Authority) types

• Root Certificate: Serves as the trust anchor for the network, signing other certificates
• Intermediate CA Certificate: Issued by the root CA to create a chain of trust also used to sign other certificates below the root level
• Enrollment Certificate (ECert): Issued to entities when they join the network for identity authentication
• TLS Certificate: Used to secure communications between network entities through Transport Layer Security (TLS)
• Transaction Certificate (TCert): Used for conducting transactions, allowing users to maintain privacy
• Signing Certificate: Specifically used to sign transactions and messages to verify the message's origin and integrity
• Revocation List: Indicates revoked certificates before expiration

CA Features

• Certificate based Network Control:

  • Restricts access to private channels, applications and data
  • Allows for permission based access control within the network

• Custom permission based access

  • Root cert, e-cert, t-cert are provided by default
  • Custom certificates for specific access

• -- Access to only one specific channel

• -- Access to multiple channels

Membership Service Provider (MSP) details

• MSP is an interface to support credentials architectures
• MSP handles these functions:
  • Identity format
  • User credential validation
  • User credential revocation
  • Signature generation and verification

MSP implementation

• The MSP is installed for peer authentication and authorization
• Each MSP needs a unique MSP ID
• Default implementation has these parameters:
  • self-signed certs to represent CAs,
  • admin certs (X.509),
  • member lists,
  • certificate revocation lists (CRLs),
  • intermediate TLS CAs certs,
  • TLS root certs

MSP Identity Rule requires validity and authorization to satisfy:

• X.509 certificate
• Not included in any CRL
• Lists organizational units following the X.509 cert structure

MSP Certificates

• Generates an X.509 cert through Openssl, Cryptogen or Hyperledger Fabric CA
• To setup a local MSP you need a folder containing these subfolders and files: admincerts, intermediatecerts, tlscacerts, cacerts, crls, signcerts, Tlsintermediatecerts, and a config.yaml file

Hyperledger Fabric setup

• Set-up involves MacOS or VM-ware/Virtualbox with Ubuntu and the fabric samples
• Install all pre-requisites before other actions
• A link to download instructions: https://hyperledger-fabric.readthedocs.io/en/release-2.5/

Introduction to Hyperledger

• Hyperledger is opensource and framework for constructing you own blockchain
• Hyperledger has Key points:
• -- Enterprise grade blockchain networks
• -- Created by Linux Foundation in 2015
• -- Supported by > 100 members including Intel, IBM, Samsung, J.P.Morgan

What is Hyperledger Besu?

• Hyperledger Besu is developed for enterprise use on both public and private permissioned networks
• Can be used on Rinkeby, Ropston, Goerli test network
• Support for PoW (Proof-of-Work) for authorization
• Authorization is primarily suited for sophisticated authorization in consortium networks

Hyperledger Fabric

• Hyperledger Fabric by IBM is one of the Blockchain framework for applications using modular architecture
• Modules like consensus and membership services are plug-and-play, so it's very adaptable across a wide range
• Chaincode has smart contracts, and uniquely adapts to maintain privacy

Hyperledger Indy

• Designed for delivering Digital identities
• Can support with various blockchains
• Supports identity centralization with applications
• Has ZKP Support

Hyperledger Iroha

• Ihoha is configured for mobile and IoT (Internet of Things)
• Has chain and BFT consensus with sync algorithms
• Has Module distributed blockchain network for mobile and IoT
• Support for multiple signatures

Hyperledger Sawtooth

• Hyperledger Sawtooth is has a modular and scalable architecture by Intel
• Hyperledger Sawtooth has separated business rules
• Has Practical Byzantine Fault Tolerance (PBFT) and Proof of Elapsed Time (POET) for Consensus algorithm

Hyperledger Libraries

• Hyperledger Aries collaborative tool for creating, transmitting, and storing verified data while managing data
• Hyperledger Quilt is A Java version of Interledger protocol with payments
• Hyperledger Transaction reduces development work
• Hyperledger Ursa has cryptology features

What are Hyperledger functions?

• Hyperledger Avalon has specification code for EEA
• Hyperledger Cactus for enabled blockchains
• Hyperledger Caliper measures performance
• Hyperleder Cello start, maintains and completes with services
• Hyperledger Explorer analyzes data

Hyperledger Guarantees

• Hyperledger is Private and Permissioned so there is data privacy
• Hyperledger Fabric has modularized and adaptable architecture
• Hyperledger Fabric supports smart contracts
• Hyperledger Fabric supports customizable consensus

Hyperledger key functions

• Peers: Nodes responsible for Executing code, endorsement and maintains the ledger
• Service handles ordering
• Managing identities with permission
• Channels are built with members and have strong data protection

Fabric Roles

• Key parts include : peers of execution, code handling and identity protection
• Orderer is the networks operation
• Certificate Authority handles identity
• and channels handle scalability

Fabric Privacy and Scalability Using Channels

• Fabric uses channels to meet the privacy and scalability requirements for enterprise networks
• Channels authorize only privileged participants to access shared private ledgers