Blockchain and its Applications | Week 6
Session: JAN-APR 2024
Course Name: Blockchain and its Applications
Course Link: Click Here
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These are Blockchain and its Applications Assignment 6 Answers
Q1. If there are 25 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: d. 51
Q2. 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
These are Blockchain and its Applications Assignment 6 Answers
Q3. If there are 25 faulty nodes in, at least how many nodes needed to reach consensus in the Byzantine Fault Tolerance (BFT) system.
a. 72
b. 76
c. 77
d. 79
Answer: b. 76
Q4. Which are the properties of an asynchronous consensus:
a. Validity
b. Agreement
c. Termination
d. Integrity
Answer: a, b, c, d
These are Blockchain and its Applications Assignment 6 Answers
Q5. 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
Q6. 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
These are Blockchain and its Applications Assignment 6 Answers
Q7. Suppose you execute your tasks distributedly from six different systems at six different locations. For maintaining the consensus among the systems, you are using the BFT model. You found that one system is permanently failed due to a hardware fault and another system is compromised by an attacker. Does your system correctly work at all?
a. No
b. Yes, with the remaining nodes
c. Yes, with all the nodes
Answer: a. No
Q8. Which of the statements are true?
a. Paxos is based on state-machine replication
b. In Paxos, Proposers and Leamers maintain a state of the running epochs
c. In a Paxos, once a consensus is reached, Paxos cannot progress to another consensus
d. Paxos works in two rounds
Answer: a, c, d
These are Blockchain and its Applications Assignment 6 Answers
Q9. State machine replication-based consensus is used over permissioned blockchains. Select the suitable reason(s)?
a. The network is closed, and the nodes know each other, hence state replication is possible among the known nodes
b. Not need to spend power, time, or bitcoin
c. Machines can behave maliciously, hence consensus in required
d. State machine replication-based consensus is not recommended to use over permissioned blockchains.
Answer: a, b
Q10. The following code snippet from paxos algorithm belongs to which phase?
is the ID the largest I have seen so far, max id == N?
if yes
reply with an ACCEPTED message & send ACCEPTED (ID, VALUE) to all learners
if no
do not respond (or respond with a “fail” message)
a. PREPARE-PROMISE
b. PROPOSE-ACCEPT
Answer: b. PROPOSE-ACCEPT
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These are Blockchain and its Applications Assignment 6 Answers
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Session: JAN-APR 2022
Course Name: Blockchain and its Applications
Course Link: Click Here
These are Blockchain and its Applications Assignment 6 Answers
Q1. 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
Q2. 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
These are Blockchain and its Applications Assignment 6 Answers
Q3. 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
Q4. If there are 24 faulty nodes 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
These are Blockchain and its Applications Assignment 6 Answers
Q5. 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
Q6. 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 toanother consensus of the value.
d. None of the above
Answer: c. Once a consensus is reached, single Paxos consensus progresses toanother consensus of the value.
These are Blockchain and its Applications Assignment 6 Answers
Q7. Which are the properties of an asynchronous consensus:
a. Validity
b. Agreement
c. Termination
d. Integrity
Answer: a, b, c, d
Q8. Which of 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 of the above
Answer: d. All of the above
These are Blockchain and its Applications Assignment 6 Answers
Q9. 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
Q10. 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
These are Blockchain and its Applications Assignment 6 Answers
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