CompTIA SecurityX (CAS-005)Security EngineeringHard
A financial institution is designing a new blockchain-based settlement system for inter-bank transactions. Due to regulatory requirements and the need for absolute transaction finality and immutability, the system must utilize a consensus mechanism that is highly resistant to collusion among participants and ensures that all legitimate transactions are eventually recorded, even if some participants are malicious. Which consensus mechanism would be MOST appropriate for this enterprise-grade, permissioned blockchain?
- AProof of Work (PoW)
- BPractical Byzantine Fault Tolerance (PBFT)
- CProof of Elapsed Time (PoET)
- DProof of Stake (PoS)
Show answer & explanationAnswer & explanation
Correct answer: B. Practical Byzantine Fault Tolerance (PBFT)
Practical Byzantine Fault Tolerance (PBFT) is specifically designed for permissioned blockchain networks where participants are known and finite. It provides high transaction finality and can tolerate a certain number of malicious (Byzantine) nodes, making it suitable for critical enterprise applications like financial settlement systems requiring immutability and resistance to collusion.
Why the other options are wrong
- A. PoW is used in public, permissionless blockchains (like Bitcoin) and is computationally intensive, slow for high transaction throughput, and not ideal for known participants and high finality requirements.
- C. PoET is designed for permissioned blockchains, especially in Intel SGX environments, and aims for fair leader election. However, PBFT is generally preferred for its strong guarantees of finality and Byzantine fault tolerance in a known, finite set of participants.
- D. PoS is also primarily for public, permissionless blockchains, where validators are chosen based on their stake. While more energy-efficient than PoW, it doesn't offer the same level of finality or enterprise-grade fault tolerance in a permissioned setting as PBFT.
Practical Byzantine Fault Tolerance (PBFT)
A consensus algorithm for distributed systems that can tolerate Byzantine faults (malicious or arbitrary failures) among a known, finite set of participants, ensuring agreement and transaction finality.
- Suitable for permissioned blockchain networks.
- Provides immediate transaction finality.
- Can tolerate up to (n-1)/3 faulty nodes, where n is total nodes.
Memory trick: PBFT Provides Blockchain Finality and Trust.