This section contains more frequently asked Cryptography and Network Security Multiple Choice Questions Answers in the various competitive exams.
PRACTICE IT NOW TO SHARPEN YOUR CONCEPT AND KNOWLEDGE
1. The Acronym DES stands for
- Digital Evaluation System
- Digital Encryption Standard
- Digital Encryption System
- Double Encryption Standard
B. Digital Encryption Standard
2. DES works by using
- permutation and substitution on 64 bit blocks of plain text
- only permutations on blocks of 128 bits
- exclusive ORing key bits with 64 bit blocks
- 4 rounds of substitution on 64 bit blocks with 56 bit keys
A. permutation and substitution on 64 bit blocks of plain text
3. DES (i) is a symmetric key encryption method (ii) guarantees absolute security (iii) is implementable as hardware VLSI chip (iv) is a public key encryption method
- i and ii
- ii and iii
- i and iii
- iii and iv
C. i and iii
4. DES using 56 bit keys
- Cannot be broken in reasonable time using presently available computers
- Can be broken only if the algorithm is known using even slow computers.
- Can be broken with presently available high performance computers.
- It is impossible to break ever.
C. Can be broken with presently available high performance computers.
5. Triple DES uses
- 168 bit keys on 64-bit blocks of plain text
- Working on 64-bit blocks of plain text and 56 bit keys by applying DES algorithm for three rounds.
- Works with 144 bit blocks of plain text and applies DES algorithm once.
- Uses 128 bit blocks of plain text and 112 bit keys and apply DES algorithm thrice.
B. Working on 64-bit blocks of plain text and 56 bit keys by applying DES algorithm for three rounds.
6. ripple DES
- Cannot be broken in reasonable time using presently available computers.
- Can be broken only if the algorithm is known using even slow computer.
- Can be broken with presently available high performance computers.
- It is impossible to break ever.
A. Cannot be broken in reasonable time using presently available computers.
7. Triple DES
- is a symmetric key encryption method
- guarantees excellent security
- is implementable as a hardware VLSI chip
- is public key encryption method with three keys.
B. guarantees excellent security
8. Public key encryption method is a system
- which uses a set of public keys one for each participant in e-Commerce
- in which each person who wants to communicate has two keys; a private key known to him only and a public key which is publicized to enable others to send message to him.
- which uses the RSA coding system.
- which is a standard for use in e-Commerce.
B. in which each person who wants to communicate has two keys; a private key known to him only and a public key which is publicized to enable others to send message to him.
9. Public key system is useful because
- it uses two keys.
- there is no key distribution problem as public key can be kept in a commonly accessible database.
- private key can be kept secret.
- it is a symmetric key system.
B. there is no key distribution problem as public key can be kept in a commonly accessible database.
10. In public key encryption if A wants to send an encrypted message
- A encrypts message using his private key
- A encrypts message using B’s private key
- A encrypts message using B’s public key
- A encrypts message using his public key
C. A encrypts message using B’s public key
