Consensus Mechanism Vulnerabilities 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 Mechanism Vulnerabilities flashcards as text
The 'nothing-at-stake' problem in early Proof-of-Stake designs refers to what?
Answer: Validators being able to vote on multiple competing chains at no cost
Without penalties, validators can cheaply sign every competing fork, undermining consensus because they lose nothing by backing multiple chains.
How does 'slashing' address Proof-of-Stake misbehavior?
Answer: By destroying a portion of a misbehaving validator's staked funds
Slashing penalizes provably malicious actions, such as double-signing, by burning part of the offender's stake, deterring attacks.
A 'grinding attack' in PoS attempts to manipulate what?
Answer: The validator/leader selection randomness in the attacker's favor
Grinding attacks bias the pseudo-random leader-election process so the attacker is chosen more often than chance allows.
Why is verifiable random function (VRF) based leader selection preferred in modern PoS?
Answer: It produces randomness that is unpredictable yet publicly verifiable
VRFs let validators prove their selection was legitimately random without letting anyone predict or manipulate the outcome in advance.
A 'stake centralization' risk in PoS arises primarily when:
Answer: A small number of entities or staking pools control most of the stake
If a few staking pools dominate, they can collude to censor or reorganize, weakening the decentralization that secures consensus.
What does 'weak subjectivity' require of a new PoS node joining the network?
Answer: Trusting a recent, reliable checkpoint to avoid long-range attacks
New or long-offline nodes must obtain a recent trusted checkpoint so they don't accept a fraudulent rewritten history from old keys.
Inactivity leak in PoS chains like Ethereum is designed to do what?
Answer: Gradually reduce stake of offline validators so the chain can regain finality
If too many validators go offline, the inactivity leak slowly drains their stake until active validators again form a supermajority and finalize blocks.