SSCA Cryptography & PKI 2

Question 1

Which encryption mode of operation turns a block cipher into a stream cipher by XOR-ing the plaintext with an encrypted keystream?

Accepted Answer

Output Feedback (OFB)

Answer

OFB mode pre-generates a keystream from the cipher's output and XORs it with plaintext, effectively operating as a synchronous stream cipher.

Question 2

What is the Diffie-Hellman key exchange primarily used for?

Accepted Answer

Allowing two parties to establish a shared secret over an untrusted channel

Answer

Diffie-Hellman enables two parties who have no prior shared secret to jointly derive a common symmetric key over an insecure channel without transmitting the key itself.

Question 3

An administrator discovers that the same RSA key pair is used for both encryption and digital signing. What is the primary security concern?

Accepted Answer

Dual use increases attack surface and may violate key usage constraints in certificates

Answer

Using the same key pair for both encryption and signing violates the principle of key separation; compromise of one use-case (e.g., decryption oracle) can expose the signing key.

Question 4

Which hashing algorithm is currently recommended by NIST for use in digital signatures and is part of the SHA-2 family?

Accepted Answer

SHA-256

Answer

SHA-256 is part of the NIST-approved SHA-2 family with a 256-bit output, providing strong collision resistance and currently recommended for digital signatures.

Question 5

What is a Certificate Signing Request (CSR)?

Accepted Answer

A message sent to a CA containing the applicant's public key and identity information

Answer

A CSR is a standardized message (typically PKCS#10 format) that an entity sends to a CA, containing its public key and identity details to request a signed certificate.

SSCA - Systems Security Certified Administrator Practice Test

SSCA - Systems Security Certified Administrator Practice Test

SSCA Cryptography & PKI 2