CBDH CBDH Consensus & Transaction Validation 1 — Questions and Answers
Question 1: What is the primary consensus mechanism used in Hyperledger Fabric?
- Proof of Work
- Proof of Stake
- Execute-Order-Validate (EOV) (Correct answer)
- Practical Byzantine Fault Tolerance (PBFT)
Correct answer: Execute-Order-Validate (EOV)
Fabric uses an Execute-Order-Validate architecture where transactions are executed by endorsers, ordered by the ordering service, then validated by all peers.
Question 2: Which component in Hyperledger Fabric is responsible for ordering transactions into blocks?
- Endorsing peer
- Committing peer
- Ordering service (orderer) (Correct answer)
- Certificate Authority
Correct answer: Ordering service (orderer)
The ordering service receives endorsed transactions, orders them deterministically, and broadcasts blocks to all channel peers.
Question 3: What consensus algorithm does Hyperledger Fabric's Raft-based ordering service use?
- Kafka consensus
- PBFT
- Crash Fault Tolerant (CFT) Raft (Correct answer)
- Proof of Authority
Correct answer: Crash Fault Tolerant (CFT) Raft
Fabric's Raft ordering service uses the Crash Fault Tolerant (CFT) Raft algorithm, tolerating up to (n-1)/2 orderer failures.
Question 4: What is an 'endorsement policy' in Hyperledger Fabric?
- A rule defining which orderers can create blocks
- A policy specifying which peers must simulate and sign a transaction proposal (Correct answer)
- The CA policy for issuing certificates
- A rule for gossip data dissemination
Correct answer: A policy specifying which peers must simulate and sign a transaction proposal
An endorsement policy defines which organizations' peers must execute chaincode and cryptographically sign the results for a transaction to be valid.
Question 5: During Hyperledger Fabric transaction flow, what does a client do after collecting endorsements?
- Sends the proposal directly to all peers for commitment
- Submits the endorsed transaction to the ordering service (Correct answer)
- Publishes the transaction to an external blockchain
- Requests the CA to sign the transaction
Correct answer: Submits the endorsed transaction to the ordering service
After gathering sufficient endorsements, the client packages the proposal responses into a transaction envelope and submits it to the ordering service.
Question 6: What happens during the 'validate' phase of Fabric's Execute-Order-Validate flow?
- Peers simulate chaincode execution
- The orderer checks certificate validity
- Peers verify endorsement policy compliance and detect read-write set conflicts (Correct answer)
- The CA validates the transaction signature
Correct answer: Peers verify endorsement policy compliance and detect read-write set conflicts
During validation, each committing peer checks that endorsement policies are satisfied and that the read set versions match the current world state to prevent MVCC conflicts.
CBDH CBDH Consensus & Transaction Validation 1
What is the primary consensus mechanism used in Hyperledger Fabric?