# Cryptography and Network Security MCQ Questions And Answers

## 11. What is data encryption standard (DES)?

1. Block cipher
2. Stream cipher
3. Bit cipher
4. Byte cipher

Explanation: Block cipher is the correct answer.

## 12. The ciphers of today are called round ciphers because they involve

1. Double Rounds
2. Multiple Round
4. Single Round

Explanation: The ciphers of today are called round ciphers because they involve multiple round.

## 13. Public key system is useful because

1. It uses two keys
2. Private key can be kept secret
3. There is no key distribution problem as public key can be kept in a commonly accessible database
4. It is a symmetric key system

Explanation: Public key system is useful because there is no key distribution problem as public key can be kept in a commonly accessible database.

## 14. In cryptography, the order of letters in a message is rearranged by ________

1. Transpositional ciphers
2. Substitution ciphers
3. Both (A) and (B)

Explanation: In Transpositional ciphers, the order of letters in a plaintext message is shuffled using a pre-defined method. Some of such ciphers are Rail fence ciphers and columnar transposition and hence, option A is correct.

## 15. Why did SSL certificate require in HTTP?

1. For making security weak
2. For making information movefaster
3. For sending and receiving emails unencrypted
4. For encrypted data sent over http protocol

Explanation: For encrypted data sent over http protocol, SSL certificate require in HTTP.

Data Structure MCQ Questions and Answers

## 16. We use cryptography term to transforming messages to make them

1. Secure and immune to idle
2. Secure and immune to change
3. Secure and immune to defend
4. Secure and immune to attacks

Explanation: We use cryptography term to transforming messages to make them Secure and immune to attacks.

## 17. A/an ________ algorithm transforms ciphertext to plaintext

1. Encryption
2. Decryption
3. Both (A) and (B)
4. None of the above

Explanation: A Decryption algorithm transforms ciphertext to plaintext. So, option B is correct.

## 18. In symmetric-key cryptography, the same key is used by

1. Both Party
2. One Party
3. Third Party
4. Multi Party

Explanation: In symmetric-key cryptography, the same key is used by Both Party. So, option A is correct.

## 19. Symmetric key encryption is also called as?

1. Public key encryption
2. Private key encryption
3. Both (A) and (B)
4. None of the above