In this section of Data Communication and Networking – Cryptography MCQ (Multiple Choice) Based Questions and Answers,it cover the below lists of topics.All the Multiple Choice Questions and Answers (MCQs) have been compiled from the book of Data Communication and Networking by The well known author behrouz forouzan.

**This Section covers below lists of topics.**

- Cryptography MCQ.

**Cryptography multiple choice questions and answers MCQs**

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

- Cryptography
- Cryptoanalysis
- either (a) or (b)
- neither (a) nor (b)

**2. The ________is the original message before transformation**

- ciphertext
- plaintext
- secret-text
- none of the above

**3. The ________ is the message after transformation**

- ciphertext
- plaintext
- secret-text
- none of the above

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

- encryption
- decryption
- either (a) or (b)
- neither (a) nor (b)

**5. A(n) ______ algorithm transforms ciphertext to plaintext**

- encryption
- decryption
- either (a) or (b)
- neither (a) nor (b)

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

- cipher
- secret
- key
- none of the above

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

- cipher
- secret
- key
- none of the above

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

- symmetric-key
- asymmetric-key
- either (a) or (b)
- neither (a) nor (b)

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

- symmetric-key
- asymmetric-key
- either (a) or (b)
- neither (a) nor (b)

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

- symmetric-key
- asymmetric-key
- either (a) or (b)
- neither (a) nor (b)

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

- private
- public
- either (a) or (b)
- neither (a) nor (b)

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

- private
- public
- either (a) or (b)
- neither (a) nor (b)

**13. A ________ cipher replaces one character with another character.**

- substitution
- transposition
- either (a) or (b)
- neither (a) nor (b)

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

- Substitution
- Transposition
- either (a) or (b)
- neither (a) nor (b)

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

- transposition
- additive
- shift
- none of the above

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

- transposition
- additive
- shift
- none of the above

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

- substitution
- transposition
- either (a) or (b)
- neither (a) nor (b)

**18. 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**

- S-box
- P-box
- T-box
- none of the above

**19. 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**

- S-box
- P-box
- T-box
- none of the above

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

- round
- circle
- square
- none of the above

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

- symmetric-key
- asymmetric-key
- either (a) or (b)
- neither (a) nor (b)

**22. DES has an initial and final permutation block and _________ rounds**

- 14
- 15
- 16
- none of the above

**23. The DES function has _______ components**

- 2
- 3
- 4
- 5

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

- 32-bit
- 48-bit
- 54-bit
- 42-bit

**25. ________ DES was designed to increase the size of the DES key**

- Double
- Triple
- Quadruple
- none of the above

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

- AEE
- AED
- AER
- AES

**27. AES has _____ different configurations**

- two
- three
- four
- five

**28. ECB and CBC are ________ ciphers**

- block
- stream
- field
- none of the above

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

- RSS
- RAS
- RSA
- RAA

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

- Diffie-Hellman
- RSA
- DES
- AES

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