Blockchain and its Applications Nptel Assignment 4 Answers
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Blockchain and its Applications Assignment 4 Answers
Blockchain and its Applications Assignment 4 Answers (JAN-APR 2025)
a) A change in the Bitcoin protocol that leads to the creation of a new version of the blockchain b) A new type of cryptocurrency that does not rely on blockchain technology c) A collaborative process for miners to resolve conflicts in the blockchain d) None of the above
Q2. Suppose a miner initially receives 100 bitcoins as a reward for successfully mining a block at time Jan 2009. The reward for mining a block is halved approximately every four years (or after every 210,000 blocks). Based on this halving process, which of the following statements are correct?
a) In Jan 2013, the miner will receive 50 bitcoins for adding a new block. b) In Jan 2018, the miner will receive 25 bitcoins for adding a new block. c) In Jan 2021, the miner will receive 12.5 bitcoins for adding a new block. d) In Jan 2024, the miner will receive 6.25 bitcoins for adding a new block.
Q3. How does the Bitcoin network prevent double spending?
a) A centralized authority will be used to verify each transaction before it is added to the blockchain. b) Relying on a proof-of-work consensus mechanism ensures that only one valid transaction is accepted. c) All transactions are stored in a centralized database that tracks each Bitcoin’s status. d) By limiting Bitcoin transactions to one per user per day.
Q4. Which of the following is a challenge of the permissionless model in blockchain?
a) Ensuring that all participants trust a central authority b) Reaching agreement (consensus) across a decentralized network of participants without a trusted third-party c) Limiting the number of participants to improve scalability d) Preventing participants from accessing the blockchain
Q7. Which of the following best describes Safety and Liveness in Bitcoin?
a) Safety ensures transactions are irreversible, while Liveness ensures transactions are eventually added. b) Safety guarantees quick transaction confirmation, while Liveness prevents forks. c) Safety prevents double-spending, while Liveness speeds up block creation. d) Safety ensures blocks are always valid, while Liveness ensures no transaction delays.
a) To validate transactions with the need for a central authority. b) To speed up transaction processing times by reducing the time needed to add new blocks. c) To make it easier for miners to add new blocks without computational work. d) To secure the network and prevent fraudulent transactions through computational difficulty.
Q10. Which of the following statements is incorrect regarding Proof of Work (PoW) in the context of forks, attacks, and the monopoly problem?
a) PoW forks can occur when two miners independently solve the puzzle at the same time, leading to a brief divergence in the blockchain. b) While PoW encourages miners to follow the longest chain, it does not prevent attacks like 51% attacks, where malicious miners can control the blockchain. c) The Monopoly Problem refers to a situation where a single miner or group controls a majority of the network’s hashing power, undermining decentralization. d) Proof of Work ensures complete decentralization by preventing any miner from controlling the majority of the hashing power.
These are Blockchain and its Applications Assignment 4 Answers
Q1. After a hard fork, the emerging two chains are incompatible. True or False? a. True b. False
Answer: a. True
Q2. Which is/are the possible example/s of a double-spending attack? a. Sammy has a total of 90 unspent bitcoins from two different transactions with an equal amount of bitcoins each. He tries to send the entire amount at a time each to Nikita and Ayush as transactions b. Brady bought a car using ‘m’ bitcoins. On delivery, the bitcoins are transferred from his wallet to the dealer’s wallet. c. Karan has 180 unspent bitcoins. He sends the equal amount each to Dev and Tarun one by one d. Deepak has 20 unspent bitcoins. He tries to transfer those 20 bitcoins to his two each of his friends simultaneously.
Answer: a, d
Q3. Blocks of a blockchain? a. Transaction data b. Hash c. Time stamp d. None of the above
Answer: a, b, c
Q4. What are some Bitcoin exchanges available in India: a. BuyUCoin b. ZebPay c. WazirX i. a and b ii. b and c iii. a and c iv. a, b and c
Answer: iv. a, b and c
These are Blockchain and its Applications Assignment 4 Answers
Q5. “We can achieve consensus with a single crash failure in a perfect asynchronous network.” This scenario is ________? a. Always true b. Sometimes true c. Can’t say d. Impossible
Q6. What is the correct order of adding a new block to blockchain i. Block Mining ii. Block propagation Block Flooding IV. Transaction Flooding a. iii, iv, ii, i b. iv, i, iii, ii c. iv, iii, ii, i d. II, I, III, IV
Answer: b. iv, i, iii, ii
These are Blockchain and its Applications Assignment 4 Answers
Q7. Double spending is reusing digital assets intentionally or inadvertently. True or False? a. True b. False
Answer: a. True
Q8. The primary difference between the permissionless and permissioned blockchain is _______? a. Hash Algorithms b. Confidentiality c. Availability d. Access control for the participants in the blockchain network
Answer: d. Access control for the participants in the blockchain network
These are Blockchain and its Applications Assignment 4 Answers
Q9. What is an advantage of a permissionless blockchain? a. It does not use disinterested third parties to secure blocks, as all participants have a vested interest. b. It is open to everyone in the world without permission and approval requirements. c. It is more resilient against fraud because it uses federated nodes to combat fraud. d. Its networks are built by for-profit companies and the working of the network is guaranteed.
Answer: b. It is open to everyone in the world without permission and approval requirements.
Q10. What is an advantage of a permissionless blockchain? a. It does not use disinterested third parties to secure blocks, as all participants have a vested interest. b. It is open to everyone in the world without permission and approval requirements. c. It is more resilient against fraud because it uses federated nodes to combat fraud. d. Its networks are built by for-profit companies and the working of the network is guaranteed.
Answer: c. It is more resilient against fraud because it uses federated nodes to combat fraud.
These are Blockchain and its Applications Assignment 4 Answers
Q1. “We can achieve consensus with a single crash failure in a perfect asynchronous network.” This scenario is? a. Always true b. Impossible c. Can’t say d. Sometimes true
Answer: b. Impossible
Q2. Which is/are the example/s of a double-spending attack? a. Anwesha has a total of 60 unspent bitcoins from two different transactions with an equal amount of bitcoins each. She sends the entire amount each to Arpita and Ankur from one of the transactions b. Bobby bought a bike using ‘t’ bitcoins. On delivery, the bitcoins are transferred from his wallet to the shopper’s wallet. Simultaneously, he uses that bitcoins for another purchase c. Bibhu has 140 unspent bitcoins. He sends the entire amount each to Deepak and Tanmay d. Deepak and Bibhu each have 70 unspent bitcoins. Both of them transfer 20 bitcoins to each other
These are Blockchain and its Applications Assignment 4 Answers
Q3. What is the correct order of adding a new block to blockchain i. Block Mining ii. Block propagation iii. Block Flooding iv. Transaction Flooding a. iii, iv, ii, i b. iv, iii, ii, i c. ii, i, iii, iv d. iv, i, iii, ii
Answer: d. iv, i, iii, ii
Q4. Double spending is reusing digital assets intentionally or inadvertently True or False? a. True b. False
Answer: a. True
These are Blockchain and its Applications Assignment 4 Answers
Q5. In the blockchain, cryptography ensures the authenticity of a transaction and also helps prevent double-spend. Is the above statement True or False? a. True b. False
Answer: b. False
Q6. What are Bitcoin exchanges available in India: i. BuyUCoin ii. ZebPay iii. WazirX a. i and ii b. ii and ii c. i and iii d. i, ii and iii
Answer: a, b, c, d
These are Blockchain and its Applications Assignment 4 Answers
Q7. The primary difference between the permissionless and permissioned blockchain is __________? a. Access control for the participants in the blockchain network b. Hash Algorithms c. Confidentiality d. Availability
Answer: a. Access control for the participants in the blockchain network
Q8. What is an advantage of a permissionless blockchain? a. It does not use disinterested third parties to secure blocks, as all participants have a vested interest. b. It is more resilient against fraud because it uses federated nodes to combat fraud. c. It is open to everyone in the world without permission and licensing requirements. d. Its networks are built by for-profit companies and the working of the network is guaranteed.
Answer: c. It is open to everyone in the world without permission and licensing requirements.
These are Blockchain and its Applications Assignment 4 Answers
Q9. After a hard fork, the emerging two chains are incompatible. True or False? a. True b. False
Answer: a. True
Q10. Bitcoin protocol runs over i. TCP ii. UDP iii. HTTP iv. HTTPS a. i, ii, iii b. i, iv c. Only i d. Only ii
Answer: c. Only i
These are Blockchain and its Applications Assignment 4 Answers
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