CBP - Certified Bitcoin Professional Bitcoin Mining and Consensus Questions and Answers 1 — Questions and Answers
Question 1: Which of the following best describes the primary purpose of the difficulty adjustment in the Bitcoin protocol?
- To increase the block reward for miners as more join the network.
- To maintain a consistent block generation time of approximately 10 minutes. (Correct answer)
- To decrease the total number of transactions that can fit into a single block.
- To select which miner is awarded the right to create the next block.
Correct answer: To maintain a consistent block generation time of approximately 10 minutes.
The difficulty adjustment is a core mechanism in Bitcoin's consensus protocol that recalibrates the complexity of the cryptographic puzzle miners must solve. This adjustment occurs every 2,016 blocks to ensure that, on average, a new block is added to the blockchain approximately every 10 minutes, regardless of changes in the total network hashing power.
Question 2: A mining pool operator is analyzing the latest block found by their pool. What is the very first transaction they should expect to see within the block's data structure?
- The transaction with the highest fee.
- A transaction that consolidates multiple small inputs.
- The coinbase transaction. (Correct answer)
- A transaction with a multi-signature script.
Correct answer: The coinbase transaction.
The first transaction in any valid Bitcoin block must be the coinbase transaction. This special transaction is created by the miner and serves two purposes: it allows the miner to claim the block reward (the block subsidy plus all transaction fees from the block) and it has no inputs, effectively creating new bitcoin.
Question 3: What is the core principle of Nakamoto Consensus that allows nodes to agree on the valid version of the blockchain in the event of a temporary fork?
- The chain with the most transactions is considered valid.
- The chain that was started by the earliest known miner is valid.
- The first chain to be broadcast to a majority of nodes is valid.
- The chain with the most accumulated Proof of Work (the longest chain) is considered valid. (Correct answer)
Correct answer: The chain with the most accumulated Proof of Work (the longest chain) is considered valid.
Nakamoto Consensus combines Proof of Work with the 'longest chain' rule. In the case of competing chains (a fork), the network considers the chain with the most cumulative computational work expended on it to be the authoritative one. Because more work results in a longer chain of blocks, this is often referred to as the 'longest chain rule'.
Question 4: In Bitcoin's Proof of Work system, what are miners primarily doing when they are 'mining'?
- Executing complex financial calculations to verify transaction amounts.
- Repeatedly hashing a block header with a changing nonce to find a hash below a target value. (Correct answer)
- Encrypting the list of transactions before they are added to the block.
- Solving a mathematical problem provided by the previous block's creator.
Correct answer: Repeatedly hashing a block header with a changing nonce to find a hash below a target value.
Bitcoin mining involves repeatedly running the block header through the SHA-256 hash function. Miners vary a number in the block header called a 'nonce' with each hash attempt. The goal is to find a hash output that is numerically lower than the current difficulty target. This process is computationally intensive but easy for other nodes to verify.
Question 5: A new startup begins mining Bitcoin with extremely powerful, next-generation ASIC miners, significantly increasing the total network hash rate. What is the most likely immediate consequence?
- The block reward will permanently increase.
- The average time to find a block will decrease until the next difficulty adjustment. (Correct answer)
- All other miners will be forced to shut down their operations.
- The size of each block will automatically be reduced.
Correct answer: The average time to find a block will decrease until the next difficulty adjustment.
When the total network hash rate increases, blocks are found more quickly than the 10-minute target. The system will continue to produce blocks at this faster rate until the next difficulty adjustment period (every 2,016 blocks), at which point the mining difficulty will increase to bring the average block time back to approximately 10 minutes.
Question 6: Which of the following is NOT a consensus rule that a full node would check when validating a new block?
- The block's size must be within the protocol's limits.
- The hash of the block header must be below the current target.
- The miner who created the block must be a member of a known mining pool. (Correct answer)
- All transactions within the block must be valid and contain valid digital signatures.
Correct answer: The miner who created the block must be a member of a known mining pool.
Bitcoin's consensus rules are enforced by all full nodes and are fundamental to the network's security and operation. These rules include validating block size, ensuring the Proof of Work is valid (the block hash is below the target), and verifying every single transaction. However, the identity of the miner or their affiliation with a mining pool is not a consensus rule; mining is a permissionless activity.
CBP - Certified Bitcoin Professional Bitcoin Mining and Consensus Questions and Answers 1
Which of the following best describes the primary purpose of the difficulty adjustment in the Bitcoin protocol?