3. Cryptography

Symmetric Crypto — Quiz

Test your understanding of symmetric crypto with 5 practice questions.

Practice Questions

Question 1

Which mode of operation for block ciphers uses the previous ciphertext block to generate a keystream for encrypting the next plaintext block?

Question 2

In Galois/Counter Mode (GCM), which cryptographic component is responsible for authenticating additional associated data (AAD)?

Question 3

What is the recommended minimum symmetric key length for AES to provide an adequate security margin against brute-force attacks?

Question 4

An attacker can test $2^{40}$ keys per second. Approximately how many years would it take on average to brute-force a 128-bit key? Show your calculation.

Question 5

Which advantage do stream ciphers offer over block ciphers when encrypting data?