Cryptocurrency Core Cryptographic Principles 2

Question 1

Which property ensures that a hash function output cannot be used to determine the original input?

Accepted Answer

Pre-image resistance

Answer

Pre-image resistance means it is computationally infeasible to reverse a hash and find the original input.

Question 2

What is the purpose of a nonce in cryptographic protocols?

Accepted Answer

To ensure a value is used only once, preventing replay attacks

Answer

A nonce (number used once) prevents replay attacks by ensuring each transaction or message is unique.

Question 3

In elliptic curve cryptography (ECC), what operation is considered the 'hard problem' that provides security?

Accepted Answer

Elliptic curve discrete logarithm problem

Answer

ECC security relies on the difficulty of the elliptic curve discrete logarithm problem — deriving the scalar from a point multiplication.

Question 4

What distinguishes a MAC (Message Authentication Code) from a digital signature?

Accepted Answer

MACs require a shared secret key; signatures use a public/private key pair

Answer

MACs authenticate messages using a shared secret, while digital signatures use asymmetric key pairs and provide non-repudiation.

Question 5

Which block cipher mode of operation converts a block cipher into a stream cipher?

Accepted Answer

CTR (Counter Mode)

Answer

CTR mode generates a keystream by encrypting successive counter values, effectively turning a block cipher into a stream cipher.

Cryptocurrency Practice Test