Cryptocurrency Blockchain and Consensus Mechanisms 4 — Questions and Answers
Question 1: What is a 'genesis block' in a blockchain?
- The block that contains the first smart contract ever deployed
- The very first block in a blockchain, with no predecessor (Correct answer)
- A special block that resets the chain after a hard fork
- The block produced when two miners find a valid hash simultaneously
Correct answer: The very first block in a blockchain, with no predecessor
The genesis block is block zero — hardcoded into the protocol, it has no parent hash and anchors the entire chain.
Question 2: What is the purpose of the 'difficulty adjustment' mechanism in Bitcoin?
- To reduce transaction fees during periods of network congestion
- To keep the average block time near 10 minutes regardless of total hash rate (Correct answer)
- To increase block size when block production slows below target
- To penalize mining pools that find blocks too quickly
Correct answer: To keep the average block time near 10 minutes regardless of total hash rate
Bitcoin recalibrates mining difficulty every 2,016 blocks so that blocks are produced approximately every 10 minutes even as hash rate fluctuates.
Question 3: In Ethereum's proof-of-stake, what is an 'epoch'?
- A single slot in which one validator proposes a block
- A period of 32 slots used to organize validator duties and finalization checkpoints (Correct answer)
- The waiting period before staked ETH can be withdrawn
- The time window during which slashing evidence must be submitted
Correct answer: A period of 32 slots used to organize validator duties and finalization checkpoints
An epoch consists of 32 slots (approximately 6.4 minutes total), after which the beacon chain processes validator shuffling and finalization.
Question 4: What is a 'light client' in blockchain terminology?
- A mobile wallet that only stores the last 100 blocks
- A node that downloads only block headers to verify state without storing the full chain (Correct answer)
- A read-only observer node that cannot relay transactions
- A client that connects exclusively to mining pools
Correct answer: A node that downloads only block headers to verify state without storing the full chain
Light clients use Merkle proofs and block headers to verify transactions without downloading the full blockchain, reducing resource requirements.
Question 5: What is the CAP theorem's relevance to blockchain design?
- It limits the maximum block size based on computational capacity
- It states a distributed system cannot simultaneously guarantee consistency, availability, and partition tolerance (Correct answer)
- It proves that cryptographic hash functions must be collision-resistant
- It defines the maximum number of validators a PoS network can support
Correct answer: It states a distributed system cannot simultaneously guarantee consistency, availability, and partition tolerance
The CAP theorem forces blockchain designers to trade off between consistency and availability during network partitions, influencing consensus design choices.
Question 6: What is 'selfish mining' as a blockchain attack strategy?
- Refusing to relay valid competitor blocks to gain extra time to find the next block
- Mining blocks privately and revealing them strategically to waste honest miners' work (Correct answer)
- Collecting all transaction fees by submitting transactions with zero fees
- Using renewable energy to gain a cost advantage over other miners
Correct answer: Mining blocks privately and revealing them strategically to waste honest miners' work
Selfish mining involves withholding discovered blocks and releasing them at strategic moments to invalidate honest miners' work and earn a disproportionate share of rewards.
Question 7: What does 'sharding' aim to solve in blockchain scalability?
- It reduces the size of individual transactions by compressing signature data
- It splits the blockchain into parallel sub-chains so nodes only process a subset of transactions (Correct answer)
- It allows multiple consensus algorithms to run simultaneously on one chain
- It compresses historical block data to reduce full node storage requirements
Correct answer: It splits the blockchain into parallel sub-chains so nodes only process a subset of transactions
Sharding partitions the network's workload across multiple shards, each processing its own transactions in parallel, increasing overall throughput.
Cryptocurrency Blockchain and Consensus Mechanisms 4
What is a 'genesis block' in a blockchain?