Blockchain and Crypto Blockchain Fundamentals & Architecture 1 — Questions and Answers
Question 1: What is the primary data structure that gives blockchain its name and immutability?
- A linked list of encrypted records
- A hash-linked chain of blocks referencing the previous block's hash (Correct answer)
- A binary tree of transaction records
- A relational database with append-only tables
Correct answer: A hash-linked chain of blocks referencing the previous block's hash
A blockchain is a hash-linked chain where each block contains the cryptographic hash of the previous block, making any alteration detectable.
Question 2: Approximately how often does Bitcoin's network add a new block to the chain?
- Every 1 minute
- Every 10 minutes (Correct answer)
- Every 30 minutes
- Every 60 minutes
Correct answer: Every 10 minutes
Bitcoin's difficulty adjustment algorithm targets a new block every 10 minutes by recalibrating mining difficulty every 2,016 blocks.
Question 3: What is the genesis block in a blockchain?
- The block containing the highest-value transactions
- The most recently mined block in the chain
- The first block in the blockchain with no predecessor (Correct answer)
- A special block created by the network's founder
Correct answer: The first block in the blockchain with no predecessor
The genesis block is block #0, the very first block in a blockchain, which has no previous block hash to reference.
Question 4: Which consensus mechanism does Bitcoin's network use to validate new blocks?
- Proof of Stake
- Delegated Proof of Stake
- Proof of Authority
- Proof of Work (Correct answer)
Correct answer: Proof of Work
Bitcoin uses Proof of Work, requiring miners to expend computational energy solving a cryptographic puzzle to earn the right to add the next block.
Question 5: What is a Merkle tree used for in a blockchain block?
- Storing the public keys of all network participants
- Efficiently summarizing all transactions in a block via recursive hashing (Correct answer)
- Organizing blockchain nodes in a hierarchical peer-to-peer network
- Encrypting block data before broadcast
Correct answer: Efficiently summarizing all transactions in a block via recursive hashing
A Merkle tree hashes pairs of transactions up to a single Merkle root, enabling efficient and tamper-evident verification of any transaction in the block.
Question 6: What does 'immutability' mean in the context of blockchain?
- Data can be deleted but never edited
- Once written, data cannot be altered without invalidating all subsequent blocks (Correct answer)
- Only credentialed validators may modify historical records
- All data is stored in an irreversibly encrypted format
Correct answer: Once written, data cannot be altered without invalidating all subsequent blocks
Immutability means changing any historical block changes its hash, which breaks the link to the next block and propagates invalidation through the entire subsequent chain.
Question 7: What is the purpose of a 'nonce' in Bitcoin's Proof of Work mining?
- A unique identifier assigned to each transaction by the sender
- A timestamp embedded in each block to prove chronological order
- A variable number miners increment until they find a hash meeting the difficulty target (Correct answer)
- A digital signature from the network's lead validator
Correct answer: A variable number miners increment until they find a hash meeting the difficulty target
The nonce is a 32-bit number miners repeatedly change to produce a block hash with a value below the current difficulty target.
Blockchain and Crypto Blockchain Fundamentals & Architecture 1
What is the primary data structure that gives blockchain its name and immutability?