Consensus Mechanisms Flashcards

Which consensus mechanism is used by Hyperledger Fabric to order transactions before they are committed to the ledger?

Answer: Raft or Kafka-based ordering service

Hyperledger Fabric uses a pluggable ordering service (Raft or previously Kafka) to sequence transactions into blocks before peers validate and commit them.

In a Practical Byzantine Fault Tolerant (PBFT) network with 10 nodes, what is the maximum number of faulty nodes the system can tolerate?

Answer: 3

PBFT tolerates at most f faulty nodes in a network of 3f+1 nodes, so 10 nodes can tolerate floor((10-1)/3) = 3 faulty nodes.

What is the primary purpose of the 'finality' property in blockchain consensus mechanisms?

Answer: To ensure a committed block cannot be reversed or reorganized

Finality guarantees that once a block is added to the chain, it is irrevocable and no reorganization can remove or alter it.

Ethereum's move from Proof of Work to Proof of Stake (The Merge) primarily aimed to achieve which benefit?

Answer: Reduce energy consumption by ~99.95%

The Merge transitioned Ethereum to PoS, drastically cutting energy use since validators stake ETH instead of performing energy-intensive mining.

In Delegated Proof of Stake (DPoS), token holders participate in consensus by:

Answer: Voting for a fixed set of elected delegates who produce blocks

DPoS uses a democratic voting model where token holders elect delegates (witnesses/block producers) who are responsible for block production and validation.

Which characteristic best distinguishes Proof of Authority (PoA) from Proof of Stake (PoS)?

Answer: PoA relies on verified real-world identities rather than economic stake

In PoA, consensus authority is granted to pre-approved, KYC-verified participants whose reputation is at stake rather than cryptocurrency holdings.

The 'nothing-at-stake' problem is a known vulnerability in which type of consensus mechanism?

Answer: Naive Proof of Stake implementations

In naive PoS, validators have no cost to vote on multiple competing forks simultaneously, since staking tokens on one fork doesn't preclude voting on another without slashing mechanisms.