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.

a) True

b) False

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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.

a) True

b) False

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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

a) 2.8×10^{14}

b) 4.2×10^{9}

c) 1.84×10^{19}

d) 7.2×10^{16}

View Answer

Explanation: There are 2

^{56}keys =7.2×10

^{16}.

4. The number of tests required to break the Double DES algorithm are

a) 2112

b) 2111

c) 2128

d) 2119

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Explanation: For Double DES key is 2112 bits, should require 2111 tests to break.

5. How many keys does the Triple DES algorithm use?

a) 2

b) 3

c) 2 or 3

d) 3 or 4

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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

b) 2184,2111

c) 2168,2111

d) 2168,2112

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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

a) 2^{56}

b) 2^{43}

c) 2^{55}

d) 2^{47}

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Explanation: Differential Crypt-analysis requires only 2

^{47}computations to decipher the DES algorithm.

8.Using Linear Crypt-analysis, the minimum computations required to decipher the DES algorithm is

a) 2^{48}

b) 2^{43}

c) 2^{56}

d) 2^{64}

View Answer

Explanation: Linear Crypt-analysis requires only 2

^{43}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__.