CBCP Certified Blockchain Professional (CBCP) MCQ 2 — Questions and Answers
Question 1: Which consensus mechanism requires validators to lock up cryptocurrency as collateral to participate in block creation?
- Proof of Work
- Proof of Stake (Correct answer)
- Delegated Proof of Authority
- Proof of Burn
Correct answer: Proof of Stake
Proof of Stake requires validators to stake (lock) cryptocurrency as collateral, with the probability of creating the next block proportional to the amount staked.
Question 2: In Ethereum's EVM, what is the purpose of 'gas' in transaction processing?
- It encrypts transaction data end-to-end
- It measures computational effort and prevents infinite loops (Correct answer)
- It determines the block difficulty target
- It authenticates the sender's identity
Correct answer: It measures computational effort and prevents infinite loops
Gas measures the computational effort required to execute operations on the EVM, prevents infinite loops by limiting execution, and compensates miners/validators for processing.
Question 3: What distinguishes a 'hard fork' from a 'soft fork' in blockchain protocol upgrades?
- Hard forks only affect mining nodes while soft forks affect all nodes
- Hard forks are backward-incompatible while soft forks maintain backward compatibility (Correct answer)
- Hard forks require majority stake approval while soft forks require unanimous consent
- Hard forks change transaction fees while soft forks change block size
Correct answer: Hard forks are backward-incompatible while soft forks maintain backward compatibility
A hard fork creates a permanent divergence by introducing rules that old nodes cannot validate, making it backward-incompatible, whereas a soft fork tightens rules that old nodes can still accept.
Question 4: Which data structure does Bitcoin use to efficiently prove that a specific transaction is included in a block?
- Patricia Trie
- Red-Black Tree
- Merkle Tree (Correct answer)
- B+ Tree
Correct answer: Merkle Tree
Bitcoin uses a Merkle Tree to organize transactions in a block, allowing lightweight clients to verify transaction inclusion with a Merkle proof without downloading the full block.
Question 5: In a Hyperledger Fabric network, what role does the 'Orderer' node serve?
- It stores the world state database for smart contract queries
- It validates chaincode syntax before deployment
- It establishes transaction order and creates blocks for distribution (Correct answer)
- It manages identity certificates for network participants
Correct answer: It establishes transaction order and creates blocks for distribution
The Orderer in Hyperledger Fabric collects endorsed transactions, establishes a consistent ordering, packages them into blocks, and distributes those blocks to peer nodes.
Question 6: What is the primary security property provided by digital signatures in blockchain transactions?
- Confidentiality — only the recipient can read the transaction
- Non-repudiation — the sender cannot deny authorizing the transaction (Correct answer)
- Availability — the transaction is always accessible on the network
- Integrity — the transaction data is compressed for storage
Correct answer: Non-repudiation — the sender cannot deny authorizing the transaction
Digital signatures provide non-repudiation by cryptographically proving that only the private key holder could have authorized the transaction, preventing later denial.
Question 7: Which attack vector exploits a smart contract that calls an external contract before updating its own state?
- Sybil Attack
- Eclipse Attack
- Reentrancy Attack (Correct answer)
- Front-Running Attack
Correct answer: Reentrancy Attack
A reentrancy attack occurs when a malicious contract repeatedly re-enters the vulnerable contract's function before the original call updates its balance or state, draining funds.
CBCP Certified Blockchain Professional (CBCP) MCQ 2
Which consensus mechanism requires validators to lock up cryptocurrency as collateral to participate in block creation?