Blockchain Developer Consensus Algorithms and Protocols 2

Question 1

In Practical Byzantine Fault Tolerance (PBFT), how many total nodes are required to tolerate f faulty nodes?

Accepted Answer

3f + 1

Answer

PBFT requires 3f + 1 total nodes to safely tolerate f Byzantine faults.

Question 2

What problem does the 'nothing-at-stake' issue describe in Proof of Stake systems?

Accepted Answer

Validators can cheaply vote on multiple competing chains

Answer

Nothing-at-stake means validators face no cost to validate multiple forks, undermining consensus.

Question 3

In Proof of Work, what does the 'difficulty' parameter primarily control?

Accepted Answer

The expected time to find a valid block

Answer

Difficulty adjusts how hard the hash puzzle is to keep block times roughly constant.

Question 4

Which consensus mechanism does Ethereum use after 'The Merge'?

Accepted Answer

Proof of Stake

Answer

Ethereum transitioned from Proof of Work to Proof of Stake during The Merge in 2022.

Question 5

What is a key characteristic of Delegated Proof of Stake (DPoS)?

Accepted Answer

Token holders vote for a limited set of block producers

Answer

In DPoS, stakeholders elect a small group of delegates who produce blocks on their behalf.

Blockchain Practice Test