Q.1 What is the main purpose of a blockchain in cybersecurity?
To store large amounts of data in a centralized server
To provide a secure and tamper-proof ledger
To increase internet speed
To replace antivirus software
Explanation - Blockchain provides a decentralized, immutable ledger, which ensures data integrity and security.
Correct answer is: To provide a secure and tamper-proof ledger
Q.2 Which consensus mechanism is commonly used in Bitcoin?
Proof of Stake
Proof of Work
Delegated Proof of Stake
Practical Byzantine Fault Tolerance
Explanation - Bitcoin uses Proof of Work (PoW) to validate transactions and secure the network through mining.
Correct answer is: Proof of Work
Q.3 What is a smart contract?
A physical contract stored digitally
A self-executing contract with code-defined rules
A contract validated by lawyers
A contract encrypted with RSA
Explanation - Smart contracts automatically execute when predefined conditions are met, ensuring trust and efficiency.
Correct answer is: A self-executing contract with code-defined rules
Q.4 Which property ensures that a blockchain cannot be easily altered?
Encryption
Immutability
Scalability
Transparency
Explanation - Blockchain is designed so that once data is recorded, it cannot be altered or deleted, ensuring integrity.
Correct answer is: Immutability
Q.5 What is a 51% attack in blockchain?
When 51% of transactions are legitimate
When a miner controls more than 50% of network mining power
When 51% of users vote for a new block
When half the nodes are offline
Explanation - If a miner controls the majority of network power, they can manipulate transactions and double-spend coins.
Correct answer is: When a miner controls more than 50% of network mining power
Q.6 Which blockchain type is accessible only to authorized participants?
Public blockchain
Private blockchain
Hybrid blockchain
Decentralized blockchain
Explanation - Private blockchains restrict access and are controlled by a single organization or group.
Correct answer is: Private blockchain
Q.7 What does the term 'decentralization' in blockchain mean?
Data is stored on a single server
Data is controlled by multiple nodes without a central authority
Data is encrypted using a single key
Data is accessible only to developers
Explanation - Decentralization ensures no single entity controls the network, increasing security and resilience.
Correct answer is: Data is controlled by multiple nodes without a central authority
Q.8 Which of the following is a common use of blockchain in cybersecurity?
Protecting passwords
Securing financial transactions
Detecting malware
Monitoring firewall rules
Explanation - Blockchain provides a tamper-proof ledger that ensures secure, verifiable financial transactions.
Correct answer is: Securing financial transactions
Q.9 In blockchain, what is a 'node'?
A digital wallet
A computer participating in the network
A type of cryptocurrency
A mining pool
Explanation - Nodes maintain the blockchain, validate transactions, and store copies of the ledger.
Correct answer is: A computer participating in the network
Q.10 What role does cryptography play in blockchain?
It encrypts transactions to ensure security
It speeds up network communication
It creates user interfaces
It mines new coins automatically
Explanation - Cryptography ensures that blockchain data is secure, tamper-proof, and verifiable.
Correct answer is: It encrypts transactions to ensure security
Q.11 Which of the following is NOT a benefit of blockchain in security applications?
Data immutability
Decentralization
Single point of failure
Transparency
Explanation - Blockchain eliminates single points of failure; centralization is a weakness in traditional systems.
Correct answer is: Single point of failure
Q.12 What is the purpose of a digital signature in blockchain?
To speed up mining
To validate the authenticity of transactions
To encrypt the entire blockchain
To store user passwords
Explanation - Digital signatures prove that a transaction was initiated by a legitimate private key owner.
Correct answer is: To validate the authenticity of transactions
Q.13 Which type of blockchain allows anyone to read and write transactions?
Public blockchain
Private blockchain
Consortium blockchain
Permissioned blockchain
Explanation - Public blockchains are fully open for anyone to participate, enhancing transparency and decentralization.
Correct answer is: Public blockchain
Q.14 What is 'mining' in blockchain?
Validating and adding transactions to the blockchain
Extracting cryptocurrency from wallets
Hacking nodes to gain control
Creating private keys for users
Explanation - Mining involves solving complex mathematical problems to add verified blocks to the blockchain.
Correct answer is: Validating and adding transactions to the blockchain
Q.15 Which attack exploits vulnerabilities in smart contracts?
51% attack
Reentrancy attack
Sybil attack
Phishing attack
Explanation - Reentrancy attacks occur when smart contract functions call external contracts before updating state, allowing repeated withdrawals.
Correct answer is: Reentrancy attack
Q.16 Which blockchain platform is most commonly used for smart contracts?
Bitcoin
Ethereum
Ripple
Litecoin
Explanation - Ethereum supports Turing-complete smart contracts, making it widely used for decentralized applications.
Correct answer is: Ethereum
Q.17 What is a 'fork' in blockchain?
A type of cryptographic algorithm
A split in the blockchain protocol
A method of mining coins faster
A security vulnerability
Explanation - A fork occurs when a blockchain diverges into two separate chains, often due to protocol updates or disagreements.
Correct answer is: A split in the blockchain protocol
Q.18 Which of the following best describes 'immutability' in blockchain?
Data can be updated frequently
Data cannot be altered once recorded
Data is stored on a central server
Data is encrypted with a key
Explanation - Immutability ensures the blockchain maintains integrity by preventing modifications to past transactions.
Correct answer is: Data cannot be altered once recorded
Q.19 What is the role of a 'ledger' in blockchain?
To mine cryptocurrency
To record all transactions in a secure, transparent manner
To generate private keys
To encrypt network data
Explanation - The ledger is a record of all transactions maintained by blockchain nodes, ensuring transparency and trust.
Correct answer is: To record all transactions in a secure, transparent manner
Q.20 Which mechanism helps prevent double spending in blockchain?
Cryptographic hashing
Consensus algorithms
Public key infrastructure
Data redundancy
Explanation - Consensus mechanisms like Proof of Work or Proof of Stake ensure that transactions are validated and cannot be spent twice.
Correct answer is: Consensus algorithms
Q.21 What is a 'token' in blockchain applications?
A unit of cryptocurrency or digital asset
A type of network node
A blockchain consensus algorithm
A mining reward mechanism only
Explanation - Tokens represent digital assets, cryptocurrencies, or access rights in blockchain ecosystems.
Correct answer is: A unit of cryptocurrency or digital asset
Q.22 Which blockchain type combines public and private features?
Public blockchain
Private blockchain
Hybrid blockchain
Permissionless blockchain
Explanation - Hybrid blockchains allow selective access, combining transparency of public and control of private blockchains.
Correct answer is: Hybrid blockchain
Q.23 Which term refers to a network where participants can join and leave freely?
Permissioned network
Decentralized network
Permissionless network
Private network
Explanation - In a permissionless blockchain, anyone can participate without prior approval, promoting decentralization.
Correct answer is: Permissionless network
Q.24 Which cryptographic function links blocks in a blockchain?
Encryption
Hashing
Symmetric key exchange
Digital signature
Explanation - Hash functions create unique fingerprints of each block, linking them securely and preventing tampering.
Correct answer is: Hashing
Q.25 What is 'gas' in the Ethereum blockchain?
A unit of cryptocurrency
A fee for executing smart contracts
A mining reward
A consensus protocol
Explanation - Gas is used to pay for computation and storage costs when executing smart contracts on Ethereum.
Correct answer is: A fee for executing smart contracts