Consensus Mechanisms Flashcards
7 cards from real Blockchain Technology practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Consensus Mechanisms flashcards as text
What is a 'long-range attack' in Proof of Stake?
Answer: Rewriting history from an old block using past validator keys
Attackers use old validator keys to build an alternative chain from far back in history.
In Proof of Work, what is the role of the 'difficulty' parameter?
Answer: It adjusts how hard it is to find a valid block hash
Difficulty adjusts the target hash threshold to keep block times roughly constant.
Which attack involves a miner secretly mining a longer chain then releasing it to reverse transactions?
Answer: 51% attack
A 51% attack uses majority hash power to build and reveal a longer chain that reorganizes the ledger.
What does a VRF (Verifiable Random Function) provide in consensus protocols like Algorand?
Answer: Unpredictable yet verifiable random leader selection
A VRF generates randomness that is unpredictable in advance but publicly verifiable afterward, used for secret committee selection.
In Practical Byzantine Fault Tolerance (PBFT), what are the three main phases?
Answer: Pre-prepare, prepare, commit
PBFT reaches agreement through pre-prepare, prepare, and commit message rounds among replicas.
What is the main trade-off of increasing PoW block frequency (shorter block times)?
Answer: More orphaned/stale blocks and weaker security
Faster blocks increase the rate of orphaned blocks due to propagation delays, reducing effective security.
Which consensus approach is used by Hyperledger Fabric by default for ordering?
Answer: Raft (crash fault tolerant)
Hyperledger Fabric's ordering service commonly uses Raft, a crash-fault-tolerant consensus protocol.