NPTEL Blockchain and its Applications Week 6 Topics

Blockchain and its Applications Assignment 6 Answers

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NPTEL Blockchain and its Applications Week 6 Topics

Concepts covered in NPTEL Blockchain and its Applications Week 6 are:

1. Permissioned Model​
2. ​State Machine Replication​
3. State Machine Replication as a Consensus​
4. ​Synchronous vs Asynchronous Consensus with Crash Faults​
5. Paxos – CFT Consensus​
6. Safety and Liveness of Paxos​
7. Byzantine Faults ​
8. ​Byzantine Agreement Protocols​

Blockchain and its Applications Assignment 6 Answers

1) If there are 24 faulty nodes (crash fault) in asynchronous CFT, at least how many nodes needed to reach consensus.

a. 48
b. 49
c. 50
d. 51

Answer: b. 49

Explanation:

2) In Paxos, a node can have only one role among the three roles at a time. True or False

a. False
b. True

Answer: a. False

Explanation:

3) Can we reach a consensus when there is one commander, one good lieutenant, and one faulty lieutenant in a Byzantine Generals Problem. Yes or No?

a. Yes
b. No

Answer: b. No

Explanation:

4) If there are 24 faulty nodes (crash fault) in, at least how many nodes needed to reach consensus in the Byzantine Fault Tolerance (BFT) system.

a. 72
b. 73
c. 48
d. 49

Answer: b. 73

Explanation:

5) Which are the examples of the synchronous consensus techniques?

a. RAFT
b. PAXOS
c. Byzantine General Model
d. Practical Byzantine General Model

Answer: a, b, c, d

Explanation:

6) Which of the following is false for single Paxos?

a. Paxos runs based on state-machine replication
b. Proposers and Acceptors maintain a state of the running epochs
c. Once a consensus is reached, single Paxos consensus progresses to another consensus of the value
d. None of the above

Answer: c. Once a consensus is reached, single Paxos consensus progresses to another consensus of the value

7) Which are the properties of an asynchronous consensus:

a. Validity
b. Agreement
c. Termination
d. Integrity

Answer: a, b, c, d

Explanation:

8) Which are the following is true for the permissioned model of blockchain?

a. Participants are pre-authorized
b. Membership Service providers help to obtain membership of the corresponding network
c. Security and consensus need to be established
d. All the above

Answer: d. All the above

Explanation:

9) Which of the following is/are true for smart contracts on a closed network?

a. Contract is stored on a blockchain ledger
b. Once an event is triggered, execute the codes locally on peers
c. Generate transactions as the output of execution of contract
d. The peers of the blockchain network validates the transactions and transactions are committed after successful validation.

Answer: a, b, c, d

Explanation:

10) Which of the following is/are true for basic Multi-Paxos

a. Applications often needs a continuous stream of agreed values
b. Run Multiple instances of Paxos with different round number
c. If a value has been accepted for a round process further accept requests for different value in that round
d. All of the above

Answer: a, b

Disclaimer: Chandras EDU does not guarantee the correctness of the answers. These answers are based on the data provided by the NPTEL video lectures, are just for reference, and request students to complete the assignments independently.

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