Certified Ethical Hacker Cryptography Fundamentals

Question 1

What is the fundamental difference between symmetric and asymmetric encryption?

Accepted Answer

Symmetric uses one shared key for both encryption and decryption; asymmetric uses a public-private key pair

Answer

Symmetric encryption uses a single shared secret key for both encryption and decryption (AES, DES), while asymmetric uses mathematically related public and private key pairs (RSA, ECC) where one encrypts and the other decrypts.

Question 2

What is a hash function and what properties make it cryptographically secure?

Accepted Answer

A one-way function producing a fixed-length digest; must be collision-resistant, pre-image resistant, and deterministic

Answer

A cryptographic hash function converts arbitrary input into a fixed-length output (digest) that is practically impossible to reverse, collision-resistant (no two inputs produce the same output), and deterministic (same input always produces same output).

Question 3

What is a digital certificate and what role does it play in PKI?

Accepted Answer

An electronic document binding a public key to an identity, verified by a Certificate Authority

Answer

A digital certificate (X.509) is issued by a trusted Certificate Authority, containing the entity's public key, identity information, validity period, and the CA's digital signature, enabling trust in public key authenticity.

Question 4

What is the purpose of a digital signature?

Accepted Answer

To verify the authenticity and integrity of a message by proving it came from the claimed sender and wasn't altered

Answer

A digital signature is created by hashing the message and encrypting the hash with the sender's private key, allowing anyone with the sender's public key to verify both the sender's identity and message integrity.

Question 5

What is steganography and how does it differ from encryption?

Accepted Answer

Hiding data within other files (images, audio) to conceal its existence, versus encryption which makes data unreadable

Answer

Steganography hides the existence of a message by embedding it within innocent-looking files (images, audio, video), while encryption makes the message unreadable but its existence is known. They can be combined.

Certified Ethical Hacker Practice Test

Certified Ethical Hacker Practice Test

Certified Ethical Hacker Cryptography Fundamentals