This set of Cryptography Assessment Questions focuses on “The Data Encryption Standard (DES) and It’s Strength”.
1. During decryption, we use the Inverse Initial Permutation (IP-1) before the IP.
Explanation: IP-1 is the first step and the last step is IP during decryption.
2. A preferable cryptographic algorithm should have a good avalanche effect.
Explanation: Thus statement is true as a change in one bit of the plaintext or one bit of the key should produce a change in many bits of the ciphertext. This is referred to as the avalanche effect.
3. The number of tests required to break the DES algorithm are
Explanation: There are 256 keys =7.2×1016.
4. The number of tests required to break the Double DES algorithm are
Explanation: For Double DES key is 2112 bits, should require 2111 tests to break.
5. How many keys does the Triple DES algorithm use?
c) 2 or 3
d) 3 or 4
Explanation: For Triple DES we can either have 2 or 3 keys.
Using two keys: c = Ek1(Dk2(Ek1(m)))
Using three keys: c = Ek3(Ek2(Ek1(m))).
6. In triple DES, the key size is ___ and meet in the middle attack takes ___ tests to break the key.
a) 2192 ,2112
Explanation: The key size is 2168 and meet in the middle attack takes 2112 tests to break.
7. Using Differential Crypt-analysis, the minimum computations required to decipher the DES algorithm is
Explanation: Differential Crypt-analysis requires only 247 computations to decipher the DES algorithm.
8.Using Linear Crypt-analysis, the minimum computations required to decipher the DES algorithm is
Explanation: Linear Crypt-analysis requires only 243 computations to decipher the DES algorithm.
Sanfoundry Global Education & Learning Series – Cryptography and Network Security.
To practice all areas of Cryptography Assessment Questions, here is complete set of 1000+ Multiple Choice Questions and Answers.