CISSP Cryptography 3

Question 1

Which cryptographic algorithm is specifically designed for key wrapping and protecting other cryptographic keys?

Accepted Answer

AES-KW (AES Key Wrap)

Answer

AES Key Wrap (AES-KW) is specifically designed to protect cryptographic keys by encrypting them with a key-encrypting key (KEK).

Question 2

What is the main advantage of Elliptic Curve Cryptography (ECC) over RSA for the same security level?

Accepted Answer

ECC requires smaller key sizes for equivalent security

Answer

ECC provides equivalent security to RSA with much smaller key sizes; a 256-bit ECC key offers roughly the same security as a 3072-bit RSA key.

Question 3

A message authentication code (MAC) differs from a digital signature primarily because a MAC:

Accepted Answer

Uses a shared secret key and does not provide non-repudiation

Answer

MACs use a shared symmetric key, so any party with the key could have generated it, meaning MACs cannot provide non-repudiation.

Question 4

Which padding scheme is recommended for RSA encryption to prevent attacks such as Bleichenbacher's attack?

Accepted Answer

OAEP (Optimal Asymmetric Encryption Padding)

Answer

OAEP is the modern recommended padding for RSA encryption and is resistant to Bleichenbacher's chosen-ciphertext attack that affects PKCS#1 v1.5.

Question 5

What does perfect forward secrecy (PFS) ensure in a TLS session?

Accepted Answer

Compromise of the long-term private key does not expose past session keys

Answer

PFS ensures that each session uses an ephemeral key pair, so compromising the server's private key cannot decrypt previously captured sessions.

CISSP - Certified Information Systems Security Professional Practice Test