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

2f + 1

Answer

f + 1

Answer

4f

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

Miners waste electricity

Answer

Nodes cannot reach finality

Answer

Transactions have zero fees

Question 3

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

Accepted Answer

The expected time to find a valid block

Answer

The block reward amount

Answer

The number of transactions per block

Answer

The maximum chain length

Question 4

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

Accepted Answer

Proof of Stake

Answer

Proof of Work

Answer

Proof of Authority

Answer

Delegated Proof of Stake

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

Every node mines blocks

Answer

It requires solving hash puzzles

Answer

It has no validators

Question 6

What does 'finality' mean in a blockchain consensus context?

Accepted Answer

The point at which a transaction cannot be reversed

Answer

The last block ever produced

Answer

The total supply cap

Answer

The end of a mining epoch

Question 7

Which attack involves an entity controlling more than half of a network's mining or staking power?

Accepted Answer

51% attack

Answer

Sybil attack

Answer

Eclipse attack

Answer

Replay attack