CBCP Consensus Mechanisms and Mining Questions and Answers

Question 1

A miner successfully solves the cryptographic puzzle for a new block on a Proof-of-Work blockchain. However, due to network latency, another miner's valid block is accepted onto the main chain first. What is the term for the first miner's now-discarded block?

Accepted Answer

Stale Block

Answer

A stale block is a valid block that a miner successfully solves, but it is not added to the main blockchain because another valid block was accepted by the network first. This is typically due to network propagation delays. The miner of a stale block does not receive the block reward or transaction fees.

Question 2

In a Delegated Proof of Stake (DPoS) consensus mechanism, how are block producers (validators) chosen?

Accepted Answer

They are elected by token holders who cast votes.

Answer

The key feature of Delegated Proof of Stake (DPoS) is its democratic voting system. Token holders use their tokens to vote for a limited number of delegates (also called witnesses or block producers) who are responsible for validating transactions and creating new blocks. This differs from standard Proof of Stake (PoS) where any stakeholder meeting the minimum requirement can potentially be chosen to validate a block.

Question 3

A consortium wants to establish a private blockchain for settling high-value financial transactions. The network requires high throughput, low latency, and the ability to function correctly even if a minority of the known, permissioned nodes act maliciously. Which consensus mechanism is best suited for this scenario?

Accepted Answer

Practical Byzantine Fault Tolerance (PBFT)

Answer

Practical Byzantine Fault Tolerance (PBFT) is designed for permissioned networks where participants are known. It provides high throughput and low latency by eliminating the need for complex computational puzzles. Crucially, it is designed to tolerate 'Byzantine' (i.e., malicious or arbitrary) faults, ensuring the network can reach consensus as long as fewer than one-third of the nodes are faulty. This makes it ideal for high-security enterprise and consortium use cases.

Question 4

Which of the following best describes the primary purpose of the difficulty adjustment in the Bitcoin protocol?

Accepted Answer

To maintain a consistent average block time.

Answer

The difficulty adjustment is a fundamental mechanism in Bitcoin's Proof-of-Work system. It automatically modifies the complexity of the cryptographic puzzle that miners must solve. This adjustment occurs every 2,016 blocks (approximately every two weeks) to ensure that, regardless of how much total computing power (hashrate) is on the network, the average time to find a new block remains close to 10 minutes.

Question 5

A malicious actor gains control over 51% of the network hashrate on a Proof-of-Work blockchain. Which of the following actions can they now successfully execute?

Accepted Answer

Prevent specific future transactions from being confirmed.

Answer

A 51% attack gives the attacker control over the block creation process. With this majority hashrate, they can choose which transactions to include in the blocks they mine. This allows them to censor certain transactions by refusing to include them, effectively preventing them from being confirmed on the blockchain. They can also perform a double-spend by creating a private chain and later broadcasting it, but they cannot reverse old, deeply confirmed transactions or steal funds from wallets for which they do not have the private keys.

CBCP - Certified Blockchain Professional Practice Test

CBCP - Certified Blockchain Professional Practice Test

CBCP Consensus Mechanisms and Mining Questions and Answers