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Unit 1 - Practice Quiz

CSC203

1 What is the primary drawback of a centralized record-keeping system that distributed systems aim to solve?

A. High latency in data retrieval
B. Single point of failure
C. Complex data structures
D. Redundant data storage

2 In the context of distributed systems, what does DLT stand for?

A. Digital Linked Transaction
B. Distributed Ledger Technology
C. Data Linear Topology
D. Decentralized Logic Table

3 Which of the following best describes an immutable ledger?

A. A ledger that can be edited by anyone
B. A ledger that can only be edited by the administrator
C. A ledger where records cannot be altered or deleted once validated
D. A ledger that automatically deletes old records

4 In modeling faults, what is a Crash Fault?

A. A node stops functioning and does not respond
B. A node sends conflicting information to different peers
C. A node actively tries to hack the network
D. A node responds with incorrect data due to a bug

5 How does a Byzantine Fault differ from a Crash Fault?

A. Byzantine faults are caused by hardware failure only
B. Byzantine faults involve nodes behaving arbitrarily or maliciously
C. Byzantine faults only happen in centralized systems
D. Byzantine faults are easier to solve than crash faults

6 What is the Sybil Attack in the context of peer-to-peer networks?

A. An attack where a user steals private keys
B. An attack where a single adversary controls multiple fake identities
C. An attack that shuts down the internet connection
D. An attack on the hashing algorithm

7 The Byzantine Generals Problem is a metaphor for which challenge?

A. Encrypting messages between generals
B. Reaching consensus in the presence of unreliable or malicious nodes
C. Distributing food supplies to an army
D. Calculating the shortest path to a castle

8 In a system with nodes, what is the maximum number of Byzantine faulty nodes that can be tolerated to ensure consensus?

A.
B.
C.
D.

9 If a network has 4 generals, how many can be traitors for the system to still reach a reliable consensus?

A.
B. 1
C. 2
D. 3

10 Which of the following is NOT a property of a cryptographic hash function used in Blockchain?

A. Collision resistance
B. Pre-image resistance
C. Reversibility
D. Avalanche effect

11 What is a Hash Pointer?

A. A pointer to the memory address of the next block
B. A pointer to where data is stored together with a cryptographic hash of that data
C. A URL link to a digital image
D. A private key used to sign transactions

12 In a blockchain, if an attacker modifies data in Block , what happens to the hash pointers in subsequent blocks?

A. They remain unchanged
B. Only Block changes
C. All subsequent blocks () become invalid
D. The blockchain automatically corrects the data

13 What data structure is commonly used to efficiently summarize transactions within a block?

A. Linked List
B. Merkle Tree
C. Hash Map
D. Binary Search Tree

14 What is the Double Spending problem in digital cash?

A. Spending more money than you earn
B. Paying twice the amount for a product
C. Using the same single digital token to complete two different transactions
D. Sending money to the wrong address

15 Before Bitcoin, how was the double-spending problem typically solved?

A. Using Proof of Work
B. Using a trusted central clearinghouse (Third Party)
C. It was never solved
D. By trusting the users

16 Which consensus mechanism did Satoshi Nakamoto introduce to solve the Byzantine Generals Problem in a public network?

A. Proof of Stake (PoS)
B. Proof of Work (PoW)
C. Practical Byzantine Fault Tolerance (PBFT)
D. Round Robin

17 Who is the credited creator of Bitcoin?

A. Vitalik Buterin
B. Nick Szabo
C. Satoshi Nakamoto
D. David Chaum

18 What is the Genesis Block?

A. The last block in a blockchain
B. A block that contains a virus
C. The very first block in a blockchain
D. A block rejected by the consensus

19 What is the primary function of a Nonce in Bitcoin's Proof of Work?

A. To encrypt the transaction data
B. To count the number of users
C. An arbitrary number miners change to generate a hash below a specific target
D. A timestamp for the transaction

20 Which of the following is a major scalability issue in Proof of Work blockchains?

A. Too much storage space
B. Low transaction throughput (TPS)
C. Lack of security
D. Centralization of nodes

21 What is the Scalability Trilemma in blockchain?

A. You can only choose two: Decentralization, Security, Scalability
B. You can only choose two: Privacy, Speed, Cost
C. You can only choose two: Hardware, Software, Network
D. You can only choose two: Mining, Staking, Voting

22 Which technology was borrowed from Adam Back's work for Bitcoin?

A. Smart Contracts
B. Hashcash (Proof of Work)
C. Ring Signatures
D. Zero Knowledge Proofs

23 In Bitcoin, how is the 'Longest Chain Rule' used?

A. To determine which transactions are the largest
B. To resolve forks by accepting the chain with the most accumulated work
C. To decide the block size limit
D. To remove old blocks to save space

24 What does SHA-256 produce?

A. A 128-bit hash
B. A 256-bit fixed-length string
C. An encrypted version of the file
D. A compressed version of the file

25 What is a Soft Fork?

A. A backward-compatible upgrade to the blockchain protocol
B. A divergence in the chain that is permanent and non-backward compatible
C. A fork made of plastic
D. A method to clone a blockchain

26 What is the primary motivation for Distributed Record Keeping in supply chains?

A. To conceal data from competitors
B. To increase transparency and traceability among multiple stakeholders
C. To reduce the cost of internet bandwidth
D. To centralize authority

27 In the context of CAP Theorem, which two properties do typical blockchains (like Bitcoin) prioritize?

A. Consistency and Availability
B. Availability and Partition Tolerance
C. Consistency and Partition Tolerance
D. Speed and Security

28 Which of the following is a characteristic of Private Blockchains?

A. Anyone can join and read the ledger
B. Access is restricted to permissioned users
C. They utilize Proof of Work exclusively
D. They are fully decentralized

29 What is a Coinbase Transaction?

A. A transaction to buy coins from a database
B. The first transaction in a block that creates new coins for the miner
C. A transaction fee paid to the network
D. A transaction that failed verification

30 Which digital cash pioneer created eCash and focused on privacy/anonymity using blind signatures?

A. Hal Finney
B. David Chaum
C. Adam Back
D. Wei Dai

31 What prevents a user from modifying the content of a previous block in Bitcoin?

A. The timestamp
B. The computational energy required to redo the Proof of Work for that block and all subsequent blocks
C. The fear of getting banned
D. The centralized server rejects it

32 What is the role of Asymmetric Cryptography (Public/Private keys) in Blockchain?

A. To mine new blocks
B. To sign transactions and verify ownership
C. To compress the blockchain data
D. To connect to the internet

33 In a peer-to-peer network, what is Gossip Protocol?

A. A method where nodes share information randomly with peers to propagate data across the network
B. A chat room for miners
C. A security breach protocol
D. A way to gossip about price

34 What happens when a collision occurs in a hash function?

A. The system crashes
B. Two different inputs produce the same output hash
C. The hash function deletes the data
D. The inputs are automatically encrypted

35 Why is Proof of Work considered energy inefficient?

A. It requires constant internet connection
B. It requires massive computational power performing repetitive calculations
C. It uses old batteries
D. It requires manual human labor

36 What defines the Target in Bitcoin mining?

A. The number of bitcoins to be mined
B. The specific IP address of the node
C. A 256-bit number that the block hash must be less than or equal to
D. The version number of the software

37 Which of the following is an example of a State Machine Replication problem?

A. Ensuring all nodes execute the same transactions in the same order
B. Replicating hardware components
C. Copying emails to a backup server
D. Backing up a database to a USB drive

38 What is the UTXO model?

A. Universal Text Xylophone Organization
B. Unspent Transaction Output
C. User Transaction Order
D. United Token Exchange Oracle

39 In the context of Adversaries, what is a 51% Attack?

A. When 51% of users sell their coins
B. When an attacker controls more than 50% of the network's mining power
C. When the price drops by 51%
D. When 51% of nodes crash

40 The concept of Timestamping in blockchain ensures what?

A. That the transaction happens instantly
B. Proof that data existed at a specific point in time
C. That the miner gets paid
D. That the clock on the user's computer is correct

41 What is the Avalanche Effect in hashing?

A. A large input produces a small output
B. A small change in input results in a significant, unpredictable change in the output
C. The hash function becomes faster over time
D. The network collapses like an avalanche

42 Which consensus algorithm is generally considered to have the highest throughput (scalability) but potentially lower decentralization?

A. Proof of Work (PoW)
B. Delegated Proof of Stake (DPoS)
C. Nakamoto Consensus
D. Hashcash

43 Wei Dai's b-money proposal was significant because:

A. It was the first to use PoW for money issuance
B. It created the first smart contract
C. It proposed a centralized bank
D. It used physical coins

44 In a distributed system, Safety ensures that:

A. Something good eventually happens
B. Nothing bad ever happens (e.g., no two nodes decide on different values)
C. The system is fast
D. The system is energy efficient

45 In a distributed system, Liveness ensures that:

A. The system never halts and eventually produces a result
B. The system is consistent
C. The system is private
D. The system cannot be hacked

46 Why is Latency a challenge in global blockchains?

A. Light travels too slow
B. Propagation delay of blocks across the global network increases the risk of forks
C. Computers are slow
D. Miners are lazy

47 A Smart Contract is best described as:

A. A legal document scanned into a PDF
B. Self-executing code stored on a blockchain that runs when conditions are met
C. A verbal agreement between miners
D. A contract signed with AI

48 What is the Block Header?

A. The first transaction in the block
B. Metadata containing the version, previous block hash, merkle root, timestamp, and nonce
C. The title of the blockchain
D. The signature of the creator

49 Why do blockchains use Public Key Cryptography (Digital Signatures) instead of passwords?

A. Passwords are too short
B. To remove the need for a central server to store and verify passwords
C. It is cheaper
D. It looks cooler

50 The combination of P2P networking, cryptography, and consensus algorithms in blockchain results in a system that is:

A. Trustless
B. Trust-dependent
C. Managed
D. Fragile