Consensus Mechanisms Flashcards

Which consensus property is violated when two honest nodes permanently disagree on the canonical state of the blockchain?

Answer: Safety

Safety (also called consistency) is violated when honest nodes commit conflicting blocks or states, as the system should ensure no two honest nodes ever finalize different values.

A CBSA candidate is evaluating a public blockchain for a high-value asset tokenization platform. Which consensus feature is most critical for regulatory compliance?

Answer: Deterministic finality preventing transaction reversal

Asset tokenization for regulated markets requires deterministic finality so that settled transactions cannot be reversed, meeting financial regulators' settlement finality requirements.

In the context of sharding and consensus, what challenge does 'cross-shard communication' introduce?

Answer: It requires atomic coordination across shards that operate with independent consensus

Cross-shard transactions require coordination protocols to ensure atomicity across independently-consensing shards, introducing complexity around deadlocks and partial failures.

Nakamoto consensus achieves Sybil resistance in Proof of Work by tying voting power to:

Answer: Computational work (hash rate), making identity creation economically costly

PoW uses real-world energy and hardware investment as the basis for voting weight, making it prohibitively expensive to create enough fake identities (Sybils) to influence consensus.

What is the primary trade-off when increasing the number of validators in a BFT consensus protocol?

Answer: Better decentralization but exponentially higher communication overhead (O(n²))

Classical BFT protocols require all-to-all message exchange during voting phases, resulting in O(n²) message complexity that becomes a bottleneck as the validator count grows.

In Proof of Stake, what is the purpose of an 'epoch' in systems like Ethereum's Beacon Chain?

Answer: A defined time period (e.g., 32 slots) used to organize validator duties and committee assignments

An epoch groups a fixed number of slots, during which validators are shuffled into committees, attestation duties are assigned, and rewards/penalties are calculated at epoch boundaries.

Which scenario BEST illustrates the CAP theorem's impact on blockchain consensus design?

Answer: A BFT network halting rather than producing blocks when fewer than 2/3 of validators are online, sacrificing availability for consistency

BFT-based networks prioritize consistency (safety) over availability, halting block production if quorum cannot be reached, which directly reflects the CAP theorem's CP design choice.