Explanation:Bitcoin was introduced in a 2008 whitepaper by an unknown person or group of people using the name Satoshi Nakamoto.
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2What is the primary data structure used to link blocks together in the Bitcoin blockchain?
A.Linked List
B.Hash Pointers
C.Binary Search Tree
D.Relational Database
Correct Answer: Hash Pointers
Explanation:Each block contains the cryptographic hash of the previous block, effectively acting as a hash pointer that links the blocks in a chronological chain.
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3What is the average time target for mining a new block in the Bitcoin network?
A.2 minutes
B.5 minutes
C.10 minutes
D.15 seconds
Correct Answer: 10 minutes
Explanation:The difficulty of the Proof of Work puzzle is adjusted so that a new block is mined approximately every 10 minutes.
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4What is the maximum supply cap of Bitcoin?
A.100 million
B.18 million
C.21 million
D.Infinite
Correct Answer: 21 million
Explanation:The Bitcoin protocol hard-codes a limit on the total number of bitcoins that will ever exist to 21 million.
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5Which cryptographic hash function is primarily used in Bitcoin's Proof of Work?
A.SHA-3
B.Keccak-256
C.SHA-256
D.MD5
Correct Answer: SHA-256
Explanation:Bitcoin uses SHA-256 (Secure Hash Algorithm 256-bit) applied twice (SHA-256d) for its Proof of Work consensus mechanism.
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6What is a UTXO in the context of Bitcoin transactions?
A.Universal Transaction Output
B.Unspent Transaction Output
C.User Transaction Order
D.Unified Tax Operation
Correct Answer: Unspent Transaction Output
Explanation:UTXO stands for Unspent Transaction Output. It represents the amount of digital currency that remains after a transaction is executed and is available to be spent in a future transaction.
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7In the Bitcoin block header, what is the Nonce?
A.A timestamp of the transaction
B.A cryptographic signature of the sender
C.A 32-bit arbitrary number miners change to solve the PoW puzzle
D.The hash of the previous block
Correct Answer: A 32-bit arbitrary number miners change to solve the PoW puzzle
Explanation:The Nonce is a field in the block header that miners increment or change repeatedly until the resulting hash of the block header meets the difficulty target.
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8What data structure is used to summarize all transactions within a block efficiently?
A.Merkle Tree
B.Patricia Trie
C.Stack
D.Queue
Correct Answer: Merkle Tree
Explanation:A Merkle Tree is used to hash all transactions into a single Root Hash (Merkle Root), which is then included in the block header.
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9Mathematically, a valid Bitcoin block must satisfy which of the following conditions?
A.
B.
C.
D.
Correct Answer:
Explanation:For a block to be valid, the numerical value of its hash must be less than or equal to a specific Target value determined by the network difficulty.
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10How often is the Bitcoin mining difficulty adjusted?
A.Every block
B.Every 2016 blocks
C.Every 100 blocks
D.Every 210,000 blocks
Correct Answer: Every 2016 blocks
Explanation:The difficulty is adjusted every 2016 blocks (approximately every two weeks) to ensure the average block time remains around 10 minutes.
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11What happens during a Bitcoin Halving event?
A.The total supply of Bitcoin is cut in half
B.The block reward subsidy is cut in half
C.The block time is reduced by half
D.The difficulty is reduced by half
Correct Answer: The block reward subsidy is cut in half
Explanation:A Halving cuts the reward miners receive for mining a new block (the block subsidy) by 50%. This occurs every 210,000 blocks.
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12Which of the following is the smallest unit of Bitcoin?
A.Milli-bitcoin
B.Micro-bitcoin
C.Satoshi
D.Finney
Correct Answer: Satoshi
Explanation:The smallest unit of Bitcoin is the Satoshi, which represents Bitcoin.
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13What is the primary defense mechanism against Sybil attacks in Bitcoin?
A.Identity Verification (KYC)
B.Proof of Work
C.IP Address Whitelisting
D.Centralized Authority
Correct Answer: Proof of Work
Explanation:Proof of Work makes it prohibitively expensive to create multiple fake identities (nodes) to influence the network because each vote (block generation) requires computational power.
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14What rule do nodes follow when two valid blocks are mined at the same time (a temporary fork)?
A.Choose the block with the most transactions
B.Choose the block that arrived first
C.Longest Chain Rule (Chain with most cumulative work)
D.Random selection
Correct Answer: Longest Chain Rule (Chain with most cumulative work)
Explanation:Nodes follow the Longest Chain Rule (specifically, the chain with the most cumulative Proof of Work). They will wait for the next block to be found to resolve the tie.
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15What is a 51% Attack?
A.When 51% of users sell their Bitcoin
B.When a miner controls more than 50% of the network's hashrate
C.When 51% of nodes go offline
D.When the price drops by 51%
Correct Answer: When a miner controls more than 50% of the network's hashrate
Explanation:A 51% Attack occurs if a single entity controls more than half of the network's computing power, allowing them to potentially double-spend coins or halt transactions.
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16What is the Scalability Trilemma in blockchain?
A.Trade-off between Privacy, Speed, and Cost
B.Trade-off between Decentralization, Security, and Scalability
C.Trade-off between Hardware, Software, and Network
D.Trade-off between Mining, Staking, and Trading
Correct Answer: Trade-off between Decentralization, Security, and Scalability
Explanation:The Scalability Trilemma states that it is difficult for a blockchain to achieve Decentralization, Security, and Scalability simultaneously; usually, only two can be maximized.
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17Which of the following was a solution implemented to fix transaction malleability and improve block capacity in Bitcoin?
A.Ethereum Virtual Machine
B.Segregated Witness (SegWit)
C.Proof of History
D.Sharding
Correct Answer: Segregated Witness (SegWit)
Explanation:SegWit separates signature data (witness) from transaction data, fixing malleability and effectively increasing the block size limit.
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18What is the Lightning Network?
A.A new cryptocurrency faster than Bitcoin
B.A Layer-2 payment protocol for faster, cheaper Bitcoin transactions
C.A hardware device for mining
D.A centralized exchange
Correct Answer: A Layer-2 payment protocol for faster, cheaper Bitcoin transactions
Explanation:The Lightning Network is a Layer-2 scaling solution that uses off-chain payment channels to facilitate instant and low-fee transactions.
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19What is the main criticism regarding Bitcoin's Proof of Work consensus?
A.It is too centralized
B.It consumes a large amount of energy
C.It is not secure
D.It is too fast
Correct Answer: It consumes a large amount of energy
Explanation:Proof of Work requires massive computational power to solve cryptographic puzzles, leading to significant energy consumption.
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20Which type of fork results in a permanent divergence in the blockchain, requiring nodes to upgrade software to continue participating?
A.Soft Fork
B.Hard Fork
C.Temporary Fork
D.Git Fork
Correct Answer: Hard Fork
Explanation:A Hard Fork is a radical change to the protocol that makes previously invalid blocks/transactions valid (or vice-versa), requiring all users to upgrade.
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21In Proof of Stake (PoS), how is the creator of the next block chosen?
A.By solving a puzzle fastest
B.Deterministically based on wealth (stake) and/or age
C.By a central authority
D.By voting via email
Correct Answer: Deterministically based on wealth (stake) and/or age
Explanation:In PoS, validators are chosen to create blocks based on the amount of cryptocurrency they hold (stake) and are willing to 'lock up' as collateral.
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22What is the "Nothing at Stake" problem in early Proof of Stake implementations?
A.Validators have no funds
B.Validators can vote on multiple chain forks at no cost
C.Validators cannot stake enough coins
D.The network has no value
Correct Answer: Validators can vote on multiple chain forks at no cost
Explanation:The Nothing at Stake problem arises because, unlike PoW (where mining costs energy), it costs a PoS validator nothing to validate multiple conflicting chains to ensure they claim rewards on whichever one wins.
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23Which consensus mechanism relies on a reputation system where validators identify themselves?
A.Proof of Work
B.Proof of Authority (PoA)
C.Proof of Burn
D.Proof of Space
Correct Answer: Proof of Authority (PoA)
Explanation:Proof of Authority relies on a limited number of approved validators who stake their identity/reputation rather than coins or computing power.
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24What is Delegated Proof of Stake (DPoS)?
A.Stakeholders vote for delegates who validate transactions
B.Stakeholders must run their own nodes
C.A mix of PoW and PoS
D.Proof of Stake without rewards
Correct Answer: Stakeholders vote for delegates who validate transactions
Explanation:In DPoS, token holders vote for a small number of delegates (witnesses) who are responsible for validating transactions and maintaining the blockchain.
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25What is Proof of Burn?
A.Miners destroy mining rigs
B.Miners send coins to an unspendable address to earn mining rights
C.Miners burn electricity
D.Validators are removed for bad behavior
Correct Answer: Miners send coins to an unspendable address to earn mining rights
Explanation:In Proof of Burn, miners demonstrate commitment by sending coins to a verifiable 'eater' address where they cannot be spent, essentially 'burning' them to gain mining privileges.
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26Which consensus mechanism uses Intel SGX (trusted execution environments) to ensure random wait times?
A.Proof of Work
B.Proof of Elapsed Time (PoET)
C.Proof of Capacity
D.Proof of Activity
Correct Answer: Proof of Elapsed Time (PoET)
Explanation:Proof of Elapsed Time (PoET), often used in Hyperledger Sawtooth, uses secure hardware to enforce a random wait time for each node, where the node with the shortest wait time wins.
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27What is the primary scripting language used in Bitcoin?
A.Solidity
B.Python
C.Script
D.C++
Correct Answer: Script
Explanation:Bitcoin uses a language simply called Script, which is a stack-based, Forth-like language.
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28Which of the following describes the Bitcoin Scripting language?
A.Turing Complete
B.Not Turing Complete
C.Object-Oriented
D.Compiled Language
Correct Answer: Not Turing Complete
Explanation:Bitcoin Script is Not Turing Complete. It intentionally lacks loops (to prevent infinite loops and DOS attacks) and complex flow control.
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29What kind of data structure does the Bitcoin Script execution utilize?
A.Queue (FIFO)
B.Stack (LIFO)
C.Heap
D.Graph
Correct Answer: Stack (LIFO)
Explanation:Bitcoin Script is a Stack-based language, processing data using a Last-In, First-Out (LIFO) structure.
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30What is the most common transaction type in Bitcoin, sending funds to a public key hash?
A.P2SH (Pay to Script Hash)
B.P2PKH (Pay to Public Key Hash)
C.Coinbase
D.Null Data
Correct Answer: P2PKH (Pay to Public Key Hash)
Explanation:P2PKH is the standard transaction type where the sender locks funds to the hash of the recipient's public key.
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31Which opcode is used to verify a digital signature in Bitcoin Script?
A.OP_ADD
B.OP_HASH256
C.OP_CHECKSIG
D.OP_RETURN
Correct Answer: OP_CHECKSIG
Explanation:OP_CHECKSIG is the opcode that verifies that the transaction signature matches the public key and the transaction data.
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32What is the purpose of P2SH (Pay to Script Hash)?
A.To send Bitcoin to an email address
B.To allow senders to fund complex scripts (like Multisig) using a standard address format
C.To bypass transaction fees
D.To encrypt the transaction data
Correct Answer: To allow senders to fund complex scripts (like Multisig) using a standard address format
Explanation:P2SH shifts the burden of creating the script to the receiver. The sender sends to a hash of the script, and the receiver reveals the script to spend it. It is commonly used for Multisig wallets.
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33Which opcode allows storing arbitrary data (up to 80 bytes) on the Bitcoin blockchain, often making the output unspendable?
A.OP_DATA
B.OP_RETURN
C.OP_DROP
D.OP_NOP
Correct Answer: OP_RETURN
Explanation:OP_RETURN allows users to embed small amounts of data in the blockchain. The output becomes provably unspendable.
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34In a standard P2PKH script, what does the script look like for the Locking Script (ScriptPubKey)?
Explanation:The standard locking script duplicates the stack item, hashes it, compares it to the provided hash, and then checks the signature.
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35Why does Bitcoin Script NOT support loops?
A.To save storage space
B.To prevent Infinite Loop attacks (DoS)
C.Because loops are impossible in stack languages
D.To make mining faster
Correct Answer: To prevent Infinite Loop attacks (DoS)
Explanation:Loops were excluded to ensure that transaction verification is deterministic and terminates quickly, preventing Denial of Service (DoS) attacks via infinite loops.
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36What is a Multisig (Multi-signature) transaction?
A.A transaction sent to multiple people
B.A transaction requiring M out of N signatures to spend funds
C.A transaction signed multiple times by the same person
D.A transaction with no signature
Correct Answer: A transaction requiring M out of N signatures to spend funds
Explanation:Multisig scripts require a specific combination of signatures (e.g., 2 out of 3) from different private keys to authorize a transaction.
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37In the context of blockchain consensus, what does BFT stand for?
A.Binary File Transfer
B.Byzantine Fault Tolerance
C.Block Finality Time
D.Bitcoin Financial Technology
Correct Answer: Byzantine Fault Tolerance
Explanation:Byzantine Fault Tolerance is the property of a system to continue operating even if some components fail or act maliciously.
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38What is Slashing in Proof of Stake?
A.Reducing transaction fees
B.Penalizing validators by destroying a portion of their staked funds for bad behavior
C.Splitting the blockchain into shards
D.Cutting the block time
Correct Answer: Penalizing validators by destroying a portion of their staked funds for bad behavior
Explanation:Slashing is a mechanism to deter malicious behavior (like double signing) by confiscating part or all of the validator's stake.
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39What is a Coinbase Transaction?
A.A transaction on the Coinbase exchange
B.The first transaction in a block that creates new coins for the miner
C.A transaction with high fees
D.A transaction involving only coins
Correct Answer: The first transaction in a block that creates new coins for the miner
Explanation:The Coinbase Transaction is the first transaction in every block. It has no inputs and generates the block reward (subsidy + fees) for the miner.
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40Which of the following is a disadvantage of Proof of Stake compared to Proof of Work?
A.High energy consumption
B.Risk of centralization (Rich get richer)
C.Slow transaction speed
D.Requires expensive hardware
Correct Answer: Risk of centralization (Rich get richer)
Explanation:A common criticism of PoS is that it may lead to centralization because those with the most money earn the most rewards, compounding their wealth ('Rich get richer').
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41What is the size of a Bitcoin block header?
A.1 MB
B.80 Bytes
C.32 Bytes
D.1024 Bytes
Correct Answer: 80 Bytes
Explanation:The Bitcoin block header is exactly 80 bytes, consisting of version, previous block hash, merkle root, timestamp, difficulty target, and nonce.
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42In Bitcoin Script, what does OP_DUP do?
A.Deletes the top item
B.Duplicates the top item on the stack
C.Decodes the transaction
D.Double spends the coin
Correct Answer: Duplicates the top item on the stack
Explanation:OP_DUP pops the top item off the stack, and then pushes two copies of that item back onto the stack.
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43What is Proof of Space (also known as Proof of Capacity)?
A.Consensus based on the amount of RAM used
B.Consensus based on allocating hard drive space
C.Consensus based on physical office space
D.Consensus based on network bandwidth
Correct Answer: Consensus based on allocating hard drive space
Explanation:Proof of Space/Capacity allows miners to use available hard drive space to store pre-computed hashes (plots) to participate in consensus, rather than using computing power.
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44Which attack involves a user secretly mining a chain longer than the public chain and releasing it later to reverse transactions?
A.Sybil Attack
B.Selfish Mining
C.Eclipse Attack
D.Dusting Attack
Correct Answer: Selfish Mining
Explanation:Selfish Mining involves a miner holding back valid blocks to gain a head start on the next block, potentially invalidating the honest chain's work and earning more rewards.
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45What ensures the immutability of the Bitcoin blockchain history?
A.Legal contracts
B.The Timestamp
C.Chaining of block hashes and Proof of Work
D.The IP addresses of miners
Correct Answer: Chaining of block hashes and Proof of Work
Explanation:Immutability is secured because changing an old block would require re-doing the Proof of Work for that block and every subsequent block, which is computationally infeasible.
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46What does the term 'Difficulty Target' represent in Bitcoin?
A.The number of miners
B.The price of Bitcoin
C.A 256-bit number that the block hash must be below
D.The version of the software
Correct Answer: A 256-bit number that the block hash must be below
Explanation:The Difficulty Target is a numerical value. To mine a block, the SHA-256 hash of the header must be numerically lower than this target.
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47When a Bitcoin transaction is broadcast, where does it go before being included in a block?
A.The Blockchain
B.The Mempool (Memory Pool)
C.The Wallet
D.The Archive
Correct Answer: The Mempool (Memory Pool)
Explanation:Unconfirmed transactions wait in the Mempool of connected nodes until a miner selects them to include in a new block.
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48Which statement regarding Bitcoin addresses is true?
A.They are identical to the Public Key
B.They are a hash of the Public Key with a checksum
C.They are the same as the Private Key
D.They are generated by the miners
Correct Answer: They are a hash of the Public Key with a checksum
Explanation:A Bitcoin address is derived by hashing the public key (SHA-256 and RIPEMD-160), adding a version byte and a checksum, and encoding it (Base58).
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49What is the role of the Witness data in SegWit?
A.It stores the timestamp
B.It stores the transaction signatures/scripts separately from the transaction ID calculation
C.It monitors the network for fraud
D.It acts as a backup of the blockchain
Correct Answer: It stores the transaction signatures/scripts separately from the transaction ID calculation
Explanation:The Witness field holds the signature data. Moving this out of the main block calculation (Segregated Witness) fixes malleability and improves capacity.
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50Which of the following is considered a 'Green' alternative to Bitcoin's consensus mechanism?
A.Proof of Work (PoW)
B.Proof of Stake (PoS)
C.Ethash
D.Scrypt
Correct Answer: Proof of Stake (PoS)
Explanation:Proof of Stake is considered 'Green' because it eliminates the need for energy-intensive mining hardware, reducing electricity consumption by over 99% compared to PoW.
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