CBSA Blockchain Security and Privacy 3

Question 1

Which type of smart contract vulnerability allows an external contract to re-enter a function before the first execution completes, draining funds?

Accepted Answer

Reentrancy attack

Answer

Reentrancy attacks exploit the pattern of sending Ether before updating internal state, allowing the recipient contract to call back and repeat the withdrawal.

Question 2

What does the term 'front-running' mean in the context of blockchain security?

Accepted Answer

Miners or bots inserting transactions ahead of pending ones to profit from known price movements

Answer

Front-running exploits the public visibility of the mempool, allowing adversaries to observe pending transactions and submit their own with higher gas fees to be processed first.

Question 3

Which encryption scheme allows computations to be performed on encrypted data without decrypting it first?

Accepted Answer

Homomorphic encryption

Answer

Homomorphic encryption enables operations on ciphertexts that produce encrypted results matching the operations performed on the plaintext, preserving data privacy during computation.

Question 4

In Ethereum, which opcode is commonly blamed for the Parity multi-sig wallet freeze of 2017?

Accepted Answer

DELEGATECALL

Answer

DELEGATECALL executes library code in the context of the calling contract; the Parity freeze occurred when an attacker called DELEGATECALL to a library and invoked its suicide function, destroying it.

Question 5

A blockchain architect wants to prevent Sybil attacks in a permissionless network without proof of work. Which mechanism is most effective?

Accepted Answer

Proof of stake with economic slashing

Answer

Proof of stake requires validators to lock up economic value (stake) and introduces slashing penalties, making Sybil attacks costly because each fake identity requires real capital.

(CBSA) Certified Blockchain Solution Architect Practice Test

(CBSA) Certified Blockchain Solution Architect Practice Test

CBSA Blockchain Security and Privacy 3