Cryptocurrency Consensus Mechanisms and Mining 4 — Questions and Answers
Question 1: What is the role of 'attestations' in Ethereum's Proof of Stake consensus?
- Validators vote on which block they believe is the head of the chain, and these votes are aggregated to achieve finality (Correct answer)
- Attestations are special transactions that certify a user's identity on-chain
- Validators attest that they have sufficient ETH to cover potential slashing penalties
- Nodes certify that they have downloaded and verified the full blockchain history
Correct answer: Validators vote on which block they believe is the head of the chain, and these votes are aggregated to achieve finality
In Ethereum PoS, validators are assigned slots to attest (vote) for blocks; these aggregated attestations drive the Casper FFG finality mechanism.
Question 2: What is 'selfish mining' in Proof of Work blockchains?
- A strategy where a miner withholds discovered blocks to gain a disproportionate share of rewards relative to their hash rate (Correct answer)
- Mining only high-fee transactions and ignoring low-fee ones to maximize profit
- A solo miner refusing to join pools to keep all rewards
- Mining blocks with artificially inflated difficulty to slow down competitors
Correct answer: A strategy where a miner withholds discovered blocks to gain a disproportionate share of rewards relative to their hash rate
In selfish mining, a pool secretly mines ahead and releases blocks strategically, forcing honest miners to waste work on stale blocks, increasing the selfish pool's effective share.
Question 3: What is 'Proof of Burn' as a consensus or token distribution mechanism?
- Participants destroy (send to an unspendable address) coins to earn the right to mine or receive new tokens proportional to the burned amount (Correct answer)
- Mining rigs are destroyed after use to prove they performed real computational work
- Validators burn a portion of transaction fees as a deflationary mechanism
- Tokens are burned when a smart contract is terminated
Correct answer: Participants destroy (send to an unspendable address) coins to earn the right to mine or receive new tokens proportional to the burned amount
Proof of Burn treats burned coins as a resource — destroying value on one chain demonstrates commitment and earns mining rights or tokens on another chain (e.g., Slimcoin, initial Counterparty distribution).
Question 4: In a mining pool, what does 'pool luck' refer to?
- The ratio of actual blocks found to statistically expected blocks over a period, indicating variance in the pool's reward rate (Correct answer)
- The random selection of which pool member receives the block reward
- The percentage of the pool's hash rate contributed by the luckiest miner
- A metric showing how often the pool avoids orphaned blocks
Correct answer: The ratio of actual blocks found to statistically expected blocks over a period, indicating variance in the pool's reward rate
Pool luck >100% means the pool found more blocks than expected; <100% means fewer — it measures how actual results compare to statistical expectation over time.
Question 5: What is the 'long-range attack' in Proof of Stake systems?
- An attacker who previously held large stake rewrites blockchain history from a past point where they controlled many keys (Correct answer)
- A validator that stakes from a distant server location to reduce latency advantages of co-located validators
- An attack that targets validators who have been staking for a very long time
- A coordinated attack by multiple validators across different time zones
Correct answer: An attacker who previously held large stake rewrites blockchain history from a past point where they controlled many keys
Long-range attacks exploit PoS by using old private keys (from when an attacker held stake) to build an alternative chain from far in the past, which is cheap unlike in PoW.
Question 6: What is 'Proof of Elapsed Time' (PoET) developed by Intel?
- Validators receive a random wait time from a trusted execution environment; the first to finish waits earns the right to produce the next block (Correct answer)
- Validators must wait a set period proportional to their stake before proposing a block
- A consensus mechanism where block time is determined by the elapsed time since the last transaction
- Miners solve puzzles that measure actual elapsed CPU time rather than hash rate
Correct answer: Validators receive a random wait time from a trusted execution environment; the first to finish waits earns the right to produce the next block
PoET uses Intel SGX's Trusted Execution Environment to fairly assign random wait times; the validator with the shortest timer wins block production rights, with no energy waste.
Question 7: What is 'chain-based Proof of Stake' versus 'BFT-based Proof of Stake'?
- Chain-based PoS pseudo-randomly selects validators to extend the chain (like PoW but staked), while BFT-based uses explicit multi-round voting for immediate finality (Correct answer)
- Chain-based PoS uses a blockchain while BFT-based PoS uses a DAG structure
- Chain-based PoS requires a chain of validators to co-sign each block while BFT uses single signatures
- BFT-based PoS is only used on private blockchains while chain-based PoS is for public ones
Correct answer: Chain-based PoS pseudo-randomly selects validators to extend the chain (like PoW but staked), while BFT-based uses explicit multi-round voting for immediate finality
Chain-based PoS (e.g., early Ethereum beacon chain design) mimics PoW's probabilistic fork-choice, while BFT-based PoS (e.g., Tendermint/Cosmos) achieves one-shot finality through voting rounds.
Cryptocurrency Consensus Mechanisms and Mining 4
What is the role of 'attestations' in Ethereum's Proof of Stake consensus?