CBP Bitcoin Basics and Cryptography 2 — Questions and Answers
Question 1: What hashing algorithm does Bitcoin use for its proof-of-work mining process?
- SHA-256 (Correct answer)
- SHA-512
- MD5
- Keccak-256
Correct answer: SHA-256
Bitcoin uses SHA-256 (Secure Hash Algorithm 256-bit) as the basis for its proof-of-work mining algorithm.
Question 2: Which elliptic curve does Bitcoin use for its public-key cryptography?
- secp256k1 (Correct answer)
- secp384r1
- Curve25519
- P-521
Correct answer: secp256k1
Bitcoin uses the secp256k1 elliptic curve, which was chosen for its efficiency and security properties.
Question 3: What is the purpose of a Bitcoin address compared to a public key?
- A Bitcoin address is a hashed, encoded form of the public key for shorter, safer sharing (Correct answer)
- A Bitcoin address is identical to the public key
- A Bitcoin address is derived from the private key directly
- A Bitcoin address is a randomly generated identifier unrelated to cryptographic keys
Correct answer: A Bitcoin address is a hashed, encoded form of the public key for shorter, safer sharing
A Bitcoin address is produced by applying SHA-256 and RIPEMD-160 to the public key, then Base58Check encoding, providing a shorter and more error-resistant identifier.
Question 4: What does 'immutability' mean in the context of the Bitcoin blockchain?
- Once data is confirmed in the blockchain, it is computationally infeasible to alter it without redoing all subsequent proof-of-work (Correct answer)
- Bitcoin transactions can be reversed within 24 hours by miners
- Blocks can be modified if a majority of nodes agree
- Only the genesis block cannot be altered
Correct answer: Once data is confirmed in the blockchain, it is computationally infeasible to alter it without redoing all subsequent proof-of-work
Bitcoin's immutability comes from chained cryptographic hashes and cumulative proof-of-work, making retroactive changes computationally prohibitive.
Question 5: In Bitcoin's Script language, what does OP_CHECKSIG verify?
- That a given signature is valid for the provided public key and transaction hash (Correct answer)
- That a block header meets the difficulty target
- That a transaction fee is above the minimum threshold
- That a multisig quorum has been met
Correct answer: That a given signature is valid for the provided public key and transaction hash
OP_CHECKSIG pops a public key and signature from the stack and verifies the ECDSA signature against the transaction hash.
Question 6: What is a 'coinbase transaction' in Bitcoin?
- The first transaction in each block that creates new bitcoin and collects fees for the miner (Correct answer)
- A transaction originating from the Coinbase exchange
- A transaction that consolidates many UTXOs into one output
- The transaction that funds a Lightning Network channel
Correct answer: The first transaction in each block that creates new bitcoin and collects fees for the miner
The coinbase transaction is the mandatory first transaction in every Bitcoin block, through which miners receive the block subsidy plus transaction fees.
Question 7: What is the maximum size of a standard Bitcoin block (pre-SegWit weight limit)?
- 1 MB (Correct answer)
- 2 MB
- 4 MB
- 8 MB
Correct answer: 1 MB
Bitcoin's original block size limit was 1 MB, introduced by Satoshi to prevent spam; SegWit later introduced a 4 MB block weight limit.
CBP Bitcoin Basics and Cryptography 2
What hashing algorithm does Bitcoin use for its proof-of-work mining process?