Consensus Mechanisms Flashcards

What is 'Proof of Burn' and what problem was it designed to address?

Answer: Permanently sending coins to an unspendable address to gain mining rights; addresses energy waste of PoW

Proof of Burn requires validators to 'burn' (destroy) tokens by sending them to a verifiably unspendable address, demonstrating commitment without the energy cost of PoW mining.

Which property of PBFT makes it unsuitable for large public blockchain networks?

Answer: Its O(n²) message complexity makes it unscalable to thousands of nodes

PBFT requires each node to communicate with every other node during each consensus round, resulting in O(n²) messages that become prohibitive as node count grows.

In Avalanche consensus, what is a 'snowball' query and how does it build confidence?

Answer: Repeatedly sampling random validator subsets; accumulating sequential same-color responses increases confidence

Avalanche's Snowball protocol repeatedly samples small random subsets of validators; when consecutive rounds yield the same preference, confidence in that choice grows until a threshold is reached.

What is the primary advantage of using a Verifiable Random Function (VRF) in consensus leader selection?

Answer: It allows a node to privately prove it won the lottery without revealing the result until needed

VRF allows a node to self-select as leader and generate a cryptographic proof verifiable by others, while keeping the selection secret until the block is announced — preventing targeted attacks.

In Proof of Authority (PoA) consensus, what is the trade-off compared to Proof of Work?

Answer: PoA is faster and more efficient but sacrifices decentralization by relying on a set of approved validators

PoA achieves high throughput and energy efficiency by having known, approved validators, but this means trusting those authorities, which reduces decentralization and censorship resistance.

What is 'equivocation' in the context of blockchain consensus, and why is it considered an attack?

Answer: A validator signing two different blocks at the same height, attempting to create conflicting chains

Equivocation occurs when a validator double-signs conflicting messages at the same blockchain height, which can destabilize consensus and is treated as a slashable offense in most PoS systems.

How does Stellar's Federated Byzantine Agreement (FBA) differ from traditional BFT consensus?

Answer: FBA allows each node to choose its own trust quorum slices rather than requiring global agreement on validator sets

In FBA, nodes individually define their own 'quorum slices' (trusted peers), enabling open network membership while still achieving consensus through overlapping trust relationships.