CAP Cryptography & Encryption 3

Question 1

What is the primary purpose of a Hash-based Message Authentication Code (HMAC)?

Accepted Answer

To provide both data integrity and authentication using a shared secret

Answer

HMAC combines a cryptographic hash function with a secret key to verify both the integrity and authenticity of a message.

Question 2

Under NIST SP 800-57, what is the recommended minimum RSA key size for protecting data through 2030?

Accepted Answer

2048 bits

Answer

NIST SP 800-57 recommends a minimum of 2048-bit RSA keys to provide adequate security through 2030.

Question 3

Which attack exploits weaknesses in the CBC mode of operation by manipulating ciphertext blocks to alter decrypted plaintext?

Accepted Answer

Padding oracle attack

Answer

A padding oracle attack exploits CBC mode by sending modified ciphertexts and observing padding validation errors to decrypt data without the key.

Question 4

What does 'perfect forward secrecy' (PFS) ensure in a cryptographic protocol?

Accepted Answer

Past session keys remain secure even if the long-term private key is later compromised

Answer

PFS ensures that compromise of a long-term private key does not expose previously recorded encrypted sessions, because ephemeral keys were used.

Question 5

Which algorithm is commonly used for key derivation from passwords to slow down brute-force attacks?

Accepted Answer

PBKDF2

Answer

PBKDF2 (Password-Based Key Derivation Function 2) applies a pseudorandom function many times to stretch a password, making brute-force attacks computationally expensive.

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CAP Cryptography & Encryption 3