Blockchain Security Training Consensus Mechanism Vulnerabilities 3

Question 1

The 'nothing-at-stake' problem in early Proof-of-Stake designs refers to what?

Accepted Answer

Validators being able to vote on multiple competing chains at no cost

Answer

Without penalties, validators can cheaply sign every competing fork, undermining consensus because they lose nothing by backing multiple chains.

Question 2

How does 'slashing' address Proof-of-Stake misbehavior?

Accepted Answer

By destroying a portion of a misbehaving validator's staked funds

Answer

Slashing penalizes provably malicious actions, such as double-signing, by burning part of the offender's stake, deterring attacks.

Question 3

A 'grinding attack' in PoS attempts to manipulate what?

Accepted Answer

The validator/leader selection randomness in the attacker's favor

Answer

Grinding attacks bias the pseudo-random leader-election process so the attacker is chosen more often than chance allows.

Question 4

Why is verifiable random function (VRF) based leader selection preferred in modern PoS?

Accepted Answer

It produces randomness that is unpredictable yet publicly verifiable

Answer

VRFs let validators prove their selection was legitimately random without letting anyone predict or manipulate the outcome in advance.

Question 5

A 'stake centralization' risk in PoS arises primarily when:

Accepted Answer

A small number of entities or staking pools control most of the stake

Answer

If a few staking pools dominate, they can collude to censor or reorganize, weakening the decentralization that secures consensus.

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