Blockchain and Consensus Mechanisms Flashcards
7 cards from real Cryptocurrency practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Blockchain and Consensus Mechanisms flashcards as text
What is a UTXO in the context of Bitcoin's transaction model?
Answer: Unspent Transaction Output — a discrete chunk of bitcoin available to spend
UTXOs are discrete outputs from previous transactions that can be used as inputs in new transactions, forming Bitcoin's accounting model.
How does Delegated Proof of Stake (DPoS) differ from standard Proof of Stake?
Answer: Token holders vote for a fixed set of delegates who produce blocks on their behalf
In DPoS, coin holders elect a small group of trusted delegates who are responsible for validating transactions and producing blocks.
What is 'block finality' in the context of blockchain consensus?
Answer: The point at which a block is considered irreversible and cannot be reorganized
Finality means a confirmed block is permanently settled and cannot be undone, though its definition varies — probabilistic in PoW, deterministic in some PoS systems.
In a blockchain, what is a 'chain reorganization' (reorg)?
Answer: When a longer competing chain replaces the current canonical chain
A reorg happens when nodes discover a competing chain with more accumulated work or weight, causing them to switch chains and orphan previously accepted blocks.
What is the primary security assumption behind Nakamoto consensus (Bitcoin's PoW)?
Answer: That honest miners collectively control more than 50% of the total hash rate
Nakamoto consensus is secure as long as honest participants control the majority of hash power, making an attack prohibitively expensive.
What distinguishes a 'permissioned' blockchain from a 'permissionless' one?
Answer: Permissioned blockchains restrict who can join and validate; permissionless ones are open to anyone
Permissioned blockchains require identity verification and approval to participate, making them suitable for enterprise environments, while permissionless blockchains like Bitcoin are open.
What is the 'longest chain rule' in Bitcoin?
Answer: Nodes always adopt the chain with the greatest cumulative proof-of-work as the valid chain
Bitcoin nodes follow the chain representing the most accumulated computational work, which is typically the longest chain by block count.