Blockchain Scalability and its Foundations in Distributed Systems | Week 3

Course Name: Blockchain Scalability and its Foundations in Distributed Systems

Course Link: Blockchain Scalability and its Foundations in Distributed Systems

These are Blockchain Scalability and its Foundations in Distributed Systems Week 3 Answer Coursera Quiz

Module 3 quiz

Q1. What is the message complexity of the consensus algorithm that works in the absence of failures?

O(n)
O(n²)

Answer: O(n²)

Q2. What is the communication complexity of the consensus algorithm that works in the absence of failures where b is the number of bits to encore a value?

O(bn²)
O(bn)

Answer: O(bn²)

These are Blockchain Scalability and its Foundations in Distributed Systems Week 3 Answer Coursera Quiz

Q3. What is the time complexity of the consensus algorithm that works in the absence of failures?

O(1)
O(n)

Answer: O(1)

Q4. What is the message complexity of the crash tolerant consensus algorithm?

O(f²)
O(fn²)
O(n²)
O(nf²)

Answer: O(fn²)

These are Blockchain Scalability and its Foundations in Distributed Systems Week 3 Answer Coursera Quiz

Q5. What is the communication complexity of the crash tolerant consensus algorithm when each value is represented by b bits?

O(bfn²)
O(b²fn²)
O(bfn³)

Answer: O(bfn³)

Q6. What is the time complexity of the crash tolerant consensus algorithm?

O(n)
O(f)
O(fn)
O(f+n)

Answer: O(f)

These are Blockchain Scalability and its Foundations in Distributed Systems Week 3 Answer Coursera Quiz

Q7. What is the message complexity of the Exponential Information Gathering (EIG) Byzantine fault-tolerant consensus algorithm?

O((f+1)n²)
O((f+1)²)
O(n²)
O(f+1)

Answer: O((f+1)n²)

Q8. What is the communication complexity, expressed in bits, of the Exponential Information Gathering (EIG) Byzantine fault tolerant algorithm, with b the maximum size in bits of a message?

O(bn(f+1))
O(b(f+1)ⁿ)
O(bn^f+1)
O(bn²)

Answer: O(bn^f+1)

These are Blockchain Scalability and its Foundations in Distributed Systems Week 3 Answer Coursera Quiz

Q9. What is the time complexity of the Exponential Information Gathering (EIG) Byzantine fault tolerant algorithm?

O(f+n)
O(n²)
O(f+1)
O((f+1)n²)

Answer: O(f+1)

Q10. True or False?
One cannot solve consensus with synchrony (and without authentication) if n=9 and the number of Byzantine failures is f=3.

True
False

Answer: True

These are Blockchain Scalability and its Foundations in Distributed Systems Week 3 Answer Coursera Quiz

Q11. True or False?
One cannot solve consensus with synchrony (and without authentication) if n=7 and f=2.

True
False

Answer: False

Q12. What is the number n of nodes that should run a consensus algorithm to tolerate f Byzantine nodes in a synchronous network (without authentication)?

f+1
2f+1
3f+1

Answer: 3f+1

These are Blockchain Scalability and its Foundations in Distributed Systems Week 3 Answer Coursera Quiz

Q13. True or False?
One cannot solve consensus with synchrony (and without authentication) if n=100 and f=30.

True
False

Answer: False

These are Blockchain Scalability and its Foundations in Distributed Systems Week 3 Answer Coursera Quiz

Q14. Given that the bandwidth is a limited resource, which communication complexity would allow a consensus algorithm to scale better:

O(bfn³)
O(bn²)
O(bn^f+1)

Answer: O(bn²)

These are Blockchain Scalability and its Foundations in Distributed Systems Week 3 Answer Coursera Quiz

Q15. Why is the bit complexity of EIG increasing particularly fast with the number of participants compared to other algorithms?

Mainly because one participant needs to send messages to all participants.
Mainly because participants relay the information they received previously.

Answer: Mainly because participants relay the information they received previously.

These are Blockchain Scalability and its Foundations in Distributed Systems Week 3 Answer Coursera Quiz

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