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

Integer overflow

Answer

Front-running

Answer

Denial of service via gas limit

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

Deploying a contract before the network upgrade

Answer

Submitting multiple conflicting transactions simultaneously

Answer

Using a faster consensus algorithm

Question 3

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

Accepted Answer

Homomorphic encryption

Answer

Elliptic curve cryptography (ECC)

Answer

Symmetric AES-256

Answer

RSA-OAEP

Question 4

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

Accepted Answer

DELEGATECALL

Answer

SELFDESTRUCT

Answer

CALLCODE

Answer

STATICCALL

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

Increasing block size

Answer

Sharding

Answer

Merkle DAG

Question 6

Which privacy-enhancing feature in Monero hides the sender's address by mixing it with other public keys in a transaction?

Accepted Answer

Ring signatures

Answer

Stealth addresses

Answer

RingCT

Answer

Bulletproofs

Question 7

What is the purpose of a time-lock in a blockchain smart contract from a security perspective?

Accepted Answer

Enforcing a mandatory delay before critical actions execute, allowing detection of malicious changes

Answer

Speeding up consensus finality

Answer

Encrypting transaction data for a set period

Answer

Preventing miners from including the transaction prematurely