Consensus Mechanisms and Mining Flashcards
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Read the first 7 Consensus Mechanisms and Mining flashcards as text
What is the '51% attack' vulnerability in Proof of Work blockchains?
Answer: An entity controlling the majority of hash power can double-spend and reverse recent transactions
If a single entity controls more than 50% of the network's hash rate, they can rewrite recent blockchain history and execute double-spend attacks.
In the context of mining pools, what is a 'share'?
Answer: A proof-of-work solution that meets a lower difficulty target, submitted to demonstrate mining effort
Shares are partial proof-of-work solutions with a lower difficulty than the actual network target, used by pools to measure each miner's contributed work for reward distribution.
Which property of Byzantine Fault Tolerance (BFT) consensus describes the guarantee that all honest nodes agree on the same value?
Answer: Safety
Safety in BFT consensus ensures that no two honest nodes decide on different values, preventing forks or conflicting chain states.
What is the primary trade-off when a blockchain prioritizes 'liveness' over 'safety' in consensus?
Answer: The chain always makes progress but may temporarily allow conflicting states
Prioritizing liveness means the network keeps producing blocks even under adverse conditions, but may create forks or temporary inconsistencies that require later resolution.
In Proof of Stake, what is 'nothing at stake' problem and how is it typically addressed?
Answer: Validators can vote for multiple chain forks at no cost; addressed by slashing penalties for equivocation
Without cost for voting on multiple forks, validators could support all competing chains; slashing economically punishes this behavior by destroying stake for signing conflicting blocks.
What is 'merge mining' (Auxiliary Proof of Work)?
Answer: Simultaneously mining two blockchains that use the same hashing algorithm without additional computational work
Merge mining allows miners to use the same proof-of-work computation to mine on a parent chain and auxiliary chains simultaneously, as used by Namecoin and Bitcoin.
In Hyperledger Fabric, which component is responsible for consensus on transaction ordering?
Answer: The Ordering Service (Orderer)
The Ordering Service in Hyperledger Fabric receives endorsed transactions and establishes a definitive order, creating blocks distributed to peers for commitment.