Cryptocurrency Blockchain Technology Fundamentals 2 — Questions and Answers
Question 1: What is a Merkle tree used for in a blockchain block?
- To store miner identities
- To efficiently verify transaction integrity (Correct answer)
- To encrypt wallet addresses
- To assign block timestamps
Correct answer: To efficiently verify transaction integrity
A Merkle tree hashes transactions in pairs up to a single root hash, allowing efficient and tamper-evident verification of any transaction in the block.
Question 2: Which field in a block header links it cryptographically to the previous block?
- Nonce
- Timestamp
- Previous block hash (Correct answer)
- Merkle root
Correct answer: Previous block hash
The previous block hash field contains the hash of the preceding block, creating the cryptographic chain that makes altering past blocks computationally infeasible.
Question 3: What does 'immutability' mean in the context of blockchain?
- Blocks can be edited only by validators
- Confirmed records cannot be altered without invalidating the chain (Correct answer)
- Transactions are private and unreadable
- Nodes can delete old blocks to save space
Correct answer: Confirmed records cannot be altered without invalidating the chain
Immutability means that once data is confirmed and buried under subsequent blocks, changing it requires re-mining all later blocks, making tampering practically impossible.
Question 4: In a public blockchain, who is allowed to participate as a node?
- Only approved institutions
- Anyone with the required software (Correct answer)
- Only the founding development team
- Only users who hold a minimum balance
Correct answer: Anyone with the required software
Public blockchains are permissionless, meaning anyone can download the software and join the network as a full or light node without special approval.
Question 5: What is a '51% attack' on a Proof-of-Work blockchain?
- A bug that crashes 51% of nodes
- When a single entity controls the majority of hash rate and can rewrite recent history (Correct answer)
- When 51% of users vote to change the protocol
- An exploit that steals 51% of coins in a block reward
Correct answer: When a single entity controls the majority of hash rate and can rewrite recent history
If one miner or pool controls over 50% of the network's hash rate, they can reverse recent transactions and perform double-spends, undermining chain integrity.
Question 6: What is the primary role of a 'full node' in a blockchain network?
- Mining new blocks exclusively
- Storing the complete blockchain and independently validating all transactions (Correct answer)
- Providing user wallets and private keys
- Broadcasting only unconfirmed transactions
Correct answer: Storing the complete blockchain and independently validating all transactions
Full nodes download and independently verify every block and transaction against consensus rules, serving as the backbone of network trustlessness.
Question 7: What term describes the situation when a blockchain permanently splits into two separate chains due to a protocol disagreement?
- Soft fork
- Hard fork (Correct answer)
- Chain merge
- Block orphan
Correct answer: Hard fork
A hard fork introduces backwards-incompatible rule changes, causing nodes that don't upgrade to follow a different chain, resulting in a permanent split.
Cryptocurrency Blockchain Technology Fundamentals 2
What is a Merkle tree used for in a blockchain block?