This section contains more frequently asked Cryptography and Network Security Multiple Choice Questions Answers in the various competitive exams.
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