A merchant accepts a PoW cryptocurrency for a high-value sale. The transaction is included in a block, but the block is later orphaned due to a chain reorganization. The merchant had already shipped the goods. What is the most likely outcome?

The merchant will receive the payment from the miners who orphaned the block

The merchant will not receive the payment because the transaction is no longer in the main chain

The merchant's transaction will be automatically reversed and refunded

The merchant will receive the payment once the network stabilizes

A consortium of banks is choosing between a PBFT-based blockchain and a PoW-based blockchain for settling interbank obligations. The regulator requires that settlement be final and irrevocable at the moment of confirmation. Which choice best meets this requirement?

PBFT-based blockchain with a longest-chain rule

PBFT-based blockchain, because it provides immediate finality

PoW-based blockchain with 100 confirmations

PoW-based blockchain, because it is more decentralized

A central bank digital currency (CBDC) project must choose between a PBFT-based system that provides immediate finality and a PoS-based system that provides economic finality. The system must remain available even if some validators are temporarily offline. Which trade-off is most relevant?

PBFT offers immediate finality but may halt if more than one-third of validators are offline

PoS offers immediate finality and is more available

A crypto exchange allows users to withdraw Bitcoin after 2 confirmations. A user's withdrawal is later reversed due to a reorg. To reduce the risk of such reversals without changing the blockchain, what should the exchange do?

Increase the confirmation threshold to a higher number

Ask the user to pay a higher fee

Use a different wallet provider

EC-CouncilBlockchain Fintech Certification

Domain 2Objective 4

Finality in Blockchain Consensus BFC Practice Questions (Page 9)

Part of the Consensus Mechanisms for Financial Systems domain, which makes up ~11% of our current practice bank.

45questions here

9free pages

8concepts

Questions 41–45

41foundation · easy
Which type of finality is achieved when the cost of reversing a transaction is so high that it becomes economically irrational to attempt?
Select an answer first
42expert · hard
A merchant accepts a PoW cryptocurrency for a high-value sale. The transaction is included in a block, but the block is later orphaned due to a chain reorganization. The merchant had already shipped the goods. What is the most likely outcome?
Select an answer first
43expert · hard
A consortium of banks is choosing between a PBFT-based blockchain and a PoW-based blockchain for settling interbank obligations. The regulator requires that settlement be final and irrevocable at the moment of confirmation. Which choice best meets this requirement?
Select an answer first
44expert · hard
A central bank digital currency (CBDC) project must choose between a PBFT-based system that provides immediate finality and a PoS-based system that provides economic finality. The system must remain available even if some validators are temporarily offline. Which trade-off is most relevant?
Select an answer first
45application · medium
A crypto exchange allows users to withdraw Bitcoin after 2 confirmations. A user's withdrawal is later reversed due to a reorg. To reduce the risk of such reversals without changing the blockchain, what should the exchange do?
Select an answer first

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