This is the MCQ in Cryptography from book the Data Communications and Networking 4th Edition by Behrouz A. Forouzan. If you are looking for a reviewer in **datacom**, topic in Electronics Systems and Technologies (Communications Engineering) this will definitely help you before taking the Board Exam.

#### Begin and Good luck!

**Choose the letter of the best answer in each questions.**

1. One commonly used public-key cryptography method is the ______ algorithm.

A) RSS

B) RAS

C) RSA

D) RAA

Answer: **Option C**

Solution:

2. A(n) ______ algorithm transforms ciphertext to plaintext.

A) encryption

B) decryption

C) either (a) or (b)

D) neither (a) nor (b)

Answer: **Option B**

Solution:

3. The ________ is the message after transformation.

A) ciphertext

B) plaintext

C) secret-text

D) none of the above

Answer: **Option A**

Solution:

4. A(n) _______ algorithm transforms plaintext to ciphertext.

A) encryption

B) decryption

C) either (a) or (b)

D) neither (a) nor (b)

Answer: **Option A**

Solution:

5. The ________ method provides a one-time session key for two parties.

A) Diffie-Hellman

B) RSA

C) DES

D) AES

Answer: **Option A**

Solution:

6. A(n) ______ is a keyless substitution cipher with N inputs and M outputs that uses a formula to define the relationship between the input stream and the output stream.

A) S-box

B) P-box

C) T-box

D) none of the above

Answer: **Option A**

Solution:

7. A ________ cipher replaces one character with another character.

A) substitution

B) transposition

C) either (a) or (b)

D) neither (a) nor (b)

Answer: **Option A**

Solution:

8. The ________ cipher reorders the plaintext characters to create a ciphertext.

A) substitution

B) transposition

C) either (a) or (b)

D) neither (a) nor (b)

Answer: **Option B**

Solution:

9. _______ is a round cipher based on the Rijndael algorithm that uses a 128-bit block of data.

A) AEE

B) AED

C) AER

D) AES

Answer: **Option D**

Solution:

10. The ________is the original message before transformation.

A) ciphertext

B) plaintext

C) secret-text

D) none of the above

Answer: **Option B**

Solution:

11. A modern cipher is usually a complex _____cipher made of a combination of different simple ciphers.

A) round

B) circle

C) square

D) none of the above

Answer: **Option A**

Solution:

12. The _________ attack can endanger the security of the Diffie-Hellman method if two parties are not authenticated to each other.

A) man-in-the-middle

B) ciphertext attack

C) plaintext attack

D) none of the above

Answer: **Option A**

Solution:

13. A combination of an encryption algorithm and a decryption algorithm is called a ________.

A) cipher

B) secret

C) key

D) none of the above

Answer: **Option A**

Solution:

14. In an asymmetric-key cipher, the receiver uses the ______ key.

A) private

B) public

C) either a or b

D) neither (a) nor (b)

Answer: **Option A**

Solution:

15. AES has _____ different configurations.

A) two

B) three

C) four

D) five

Answer: **Option B**

Solution:

16. DES is a(n) ________ method adopted by the U.S. government.

A) symmetric-key

B) asymmetric-key

C) either (a) or (b)

D) neither (a) nor (b)

Answer: **Option A**

Solution:

17. DES uses a key generator to generate sixteen _______ round keys.

A) 32-bit

B) 48-bit

C) 54-bit

D) 42-bit

Answer: **Option B**

Solution:

18. The Caesar cipher is a _______cipher that has a key of 3.

A) transposition

B) additive

C) shift

D) none of the above

Answer: **Option C**

Solution:

19. ECB and CBC are ________ ciphers.

A) block

B) stream

C) field

D) none of the above

Answer: **Option A**

Solution:

20. A(n) _______is a keyless transposition cipher with N inputs and M outputs that uses a table to define the relationship between the input stream and the output stream.

A) S-box

B) P-box

C) T-box

D) none of the above

Answer: **Option B**

Solution:

21. ________ DES was designed to increase the size of the DES key.

A) Double

B) Triple

C) Quadruple

D) none of the above

Answer: **Option B**

Solution:

22. ________ is the science and art of transforming messages to make them secure and immune to attacks.

A) Cryptography

B) Cryptoanalysis

C) either (a) or (b)

D) neither (a) nor (b)

Answer: **Option A**

Solution:

23. DES has an initial and final permutation block and _________ rounds.

A) 14

B) 15

C) 16

D) none of the above

Answer: **Option C**

Solution:

24. The DES function has _______ components.

A) 2

B) 3

C) 4

D) 5

Answer: **Option C**

Solution:

25. In a(n) ________ cipher, the same key is used by both the sender and receiver.

A) symmetric-key

B) asymmetric-key

C) either (a) or (b)

D) neither (a) nor (b)

Answer: **Option A**

Solution:

26. _________ ciphers can be categorized into two broad categories: monoalphabetic and polyalphabetic.

A) Substitution

B) Transposition

C) either (a) or (b)

D) neither (a) nor (b)

Answer: **Option A**

Solution:

27. The _______ cipher is the simplest monoalphabetic cipher. It uses modular arithmetic with a modulus of 26.

A) transposition

B) additive

C) shift

D) none of the above

Answer: **Option C**

Solution:

28. In an asymmetric-key cipher, the sender uses the__________ key.

A) private

B) public

C) either (a) or (b)

D) neither (a) nor (b)

Answer: **Option B**

Solution:

29. In a(n) ________ cipher, a pair of keys is used.

A) symmetric-key

B) asymmetric-key

C) either (a) or (b)

D) neither (a) nor (b)

Answer: **Option B**

Solution:

30. The _______ is a number or a set of numbers on which the cipher operates.

A) cipher

B) secret

C) key

D) none of the above

Answer: **Option C**

Solution:

31. In a(n) ________, the key is called the secret key.

A) symmetric-key

B) asymmetric-key

C) either (a) or (b)

D) neither (a) nor (b)

Answer: **Option A**

Solution:

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*credit: Behrouz A. Forouzan*

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