Blockchain Technology Core Concepts 2 — Questions and Answers
Question 1: What property ensures that once a block is added to a blockchain, its data cannot be altered without changing all subsequent blocks?
- Immutability (Correct answer)
- Scalability
- Interoperability
- Sharding
Correct answer: Immutability
Immutability is the property that makes blockchain data tamper-resistant, since each block's hash depends on the previous block's data.
Question 2: In a Merkle tree structure used in blockchain, what does the root hash represent?
- The hash of the genesis block
- A single fingerprint of all transactions in a block (Correct answer)
- The miner's public key
- The difficulty target for mining
Correct answer: A single fingerprint of all transactions in a block
The Merkle root is a single hash derived from hashing all transactions in pairs recursively, summarizing the entire transaction set.
Question 3: Which type of blockchain network restricts participation to pre-approved entities?
- Public blockchain
- Permissioned blockchain (Correct answer)
- Tokenized blockchain
- Sharded blockchain
Correct answer: Permissioned blockchain
Permissioned (or private) blockchains require participants to be authorized before joining the network.
Question 4: What is a 'genesis block' in blockchain terminology?
- The block with the highest transaction fee
- The first block in a blockchain (Correct answer)
- The block produced by the largest mining pool
- The block that triggers a hard fork
Correct answer: The first block in a blockchain
The genesis block is the very first block in a blockchain, hard-coded with no previous block reference.
Question 5: What does the nonce field in a block header primarily serve in Proof of Work?
- It stores the sender's address
- It is a number miners adjust to find a valid hash below the difficulty target (Correct answer)
- It records the transaction count
- It identifies the consensus algorithm version
Correct answer: It is a number miners adjust to find a valid hash below the difficulty target
Miners increment the nonce repeatedly until the resulting block hash meets the required difficulty target.
Question 6: How does a blockchain network achieve fault tolerance against Byzantine failures?
- By requiring all nodes to use the same hardware
- Through consensus mechanisms that require agreement among a majority of nodes (Correct answer)
- By encrypting all data with symmetric keys
- By limiting the block size to reduce errors
Correct answer: Through consensus mechanisms that require agreement among a majority of nodes
Byzantine Fault Tolerant consensus algorithms allow the network to reach agreement even if some nodes behave maliciously or fail.
Question 7: What distinguishes a hard fork from a soft fork in blockchain protocol upgrades?
- A hard fork only changes transaction fees; a soft fork changes block size
- A hard fork is backward-incompatible, creating a permanent chain split if not universally adopted (Correct answer)
- A soft fork requires all miners to upgrade immediately
- A hard fork is reversible while a soft fork is permanent
Correct answer: A hard fork is backward-incompatible, creating a permanent chain split if not universally adopted
A hard fork introduces protocol changes that old nodes cannot validate, potentially creating two separate chains if adoption is split.
Blockchain Technology Core Concepts 2
What property ensures that once a block is added to a blockchain, its data cannot be altered without changing all subsequent blocks?