CISSP Cryptography 2

Question 1

Which key exchange protocol allows two parties to establish a shared secret over an insecure channel without transmitting the secret itself?

Accepted Answer

Diffie-Hellman

Answer

Diffie-Hellman enables two parties to derive a shared secret using public values without ever transmitting the secret itself.

Question 2

A digital signature provides which two security services?

Accepted Answer

Authentication and non-repudiation

Answer

Digital signatures verify the signer's identity (authentication) and prevent the signer from denying the action (non-repudiation).

Question 3

What is the primary weakness of a one-time pad if the same pad is used more than once?

Accepted Answer

XORing two ciphertexts reveals information about plaintexts

Answer

Reusing a one-time pad allows an attacker to XOR two ciphertexts together, canceling the key and exposing a combination of the two plaintexts.

Question 4

Which mode of operation for block ciphers produces the same ciphertext for identical plaintext blocks and is considered insecure for most uses?

Accepted Answer

ECB

Answer

Electronic Codebook (ECB) mode encrypts each block independently, so identical plaintext blocks produce identical ciphertext blocks, leaking data patterns.

Question 5

In PKI, what is the purpose of a Certificate Revocation List (CRL)?

Accepted Answer

To enumerate certificates that have been invalidated before their expiry

Answer

A CRL is a signed list published by the CA that identifies certificates that have been revoked and should no longer be trusted.

CISSP - Certified Information Systems Security Professional Practice Test

CISSP - Certified Information Systems Security Professional Practice Test

CISSP Cryptography 2