Consensus Mechanisms and Mining Flashcards

What is the role of 'attestations' in Ethereum's Proof of Stake consensus?

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.

What is 'selfish mining' in Proof of Work blockchains?

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.

What is 'Proof of Burn' as a consensus or token distribution mechanism?

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).

In a mining pool, what does 'pool luck' refer to?

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.

What is the 'long-range attack' in Proof of Stake systems?

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.

What is 'Proof of Elapsed Time' (PoET) developed by Intel?

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.

What is 'chain-based Proof of Stake' versus 'BFT-based Proof of Stake'?

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.