WorksheetsHow Blockchain Works Quiz
Total questions: 15
Worksheet time: 11mins
Which of the following best describes the output of a SHA-256 hash function?
A fixed 64-bit output
A fixed 256-bit output
A variable-length string
An encrypted message
What is the key characteristic of SHA-256 that makes it useful in blockchain?
Fast encryption
Reversible function
Deterministic and collision-resistant
Variable output length
What does it mean when we say the blockchain is "immutable"?
It can be easily updated
Data once written cannot be changed
It is temporary
It is centralized
In blockchain, immutability is primarily ensured through:
Centralized servers
Regular backups
Cryptographic hashing and linking of blocks
Permissioned access
Which of the following is a key benefit of a distributed peer-to-peer (P2P) network in blockchain?
Faster central processing
Single point of failure
Increased transparency and fault tolerance
More control by one authority
In a P2P network, each node typically:
Acts as a client only
Acts as a server only
Acts as both client and server
Is dependent on a central authority
In blockchain mining, what is a “nonce”?
A random string used to secure a wallet
A fixed key to decrypt transactions
A number miners change to find a valid hash
A block identifier
The goal of mining in proof-of-work is to:
Encrypt transactions
Decrease block size
Solve a mathematical puzzle to validate a block
Create new cryptocurrencies at will
Byzantine Fault Tolerance refers to a system’s ability to:
Work offline
Tolerate failed hard drives
Reach consensus despite malicious actors
Encrypt messages
Which problem does Byzantine Fault Tolerance address in distributed systems?
Power outage
Honest majority assumption
Miscommunication or malicious nodes
Insufficient memory
What is the main purpose of consensus protocols in blockchain?
Encrypt data
Control network access
Ensure all nodes agree on a single agreement
Distribute rewards
Proof of Work (PoW) requires participants to:
Lock up cryptocurrency as stake
Solve complex mathematical problems
Vote on transactions
Submit identity proofs
Proof of Stake (PoS) selects validators based on:
Time spent online
Size of the block
Amount of cryptocurrency held
Speed of internet connection
What protects a blockchain from a “51% attack”?
High bandwidth
A single controlling authority
Distributed consensus mechanisms
Random nonce generation
In the event of competing chains (forks), the network usually:
Stops operating
Chooses the shortest chain
Chooses the chain with the most work or stake
Duplicates all transactions
