Pretty Good Privacy

Digital Communications Systems

This set of Digital Communications Multiple Choice Questions & Answers (MCQs) focuses on “Pretty good privacy”.

1. Pretty good privacy (PGP) security system uses
a) Public key cryptosystem
b) Private key cryptosystem
c) Public & Private key cryptosystem
d) None of the mentioned

2. Public key cryptosystem is used for the encryption of
a) Messages
b) Session key
c) Session key & Messages
d) None of the mentioned

3. For digital signatures private key cryptosystem is used.
a) True
b) False

4. Data compression includes
a) Removal of redundant character
b) Uniform distribution of characters
c) Removal of redundant character & Uniform distribution of characters
d) None of the mentioned

5. PGP offers _____ block ciphers for message encryption.
a) Triple-DES
b) CAST
c) IDEA
d) All of the mentioned

6. Which block cipher has key length of 128 bits?
a) IDEA
b) CAST
c) IDEA & CAST
d) None of the mentioned

7. These three ciphers can operate of ______ of plaintext and cipher text.
a) 128 bit blocks
b) 64 bit blocks
c) 256 bit blocks
d) 156 bit blocks

8. The key size of DES is
a) 56 bits
b) 64 bits
c) 128 bits
d) 168 bits

9. Which operation is used in encryption using IDEA?
a) Addition modulo 216
b) Bit wise XOR
c) Addition modulo 216 & Bit wise XOR
d) None of the mentioned

10. What is the key size allowed in PGP?
a) 1024-1056
b) 1024-4056
c) 1024-4096
d) 1024-2048

11. Which algorithm is used for public key encryption?
a) RSA
b) Diffie-Hellman
c) RSA & Diffie-Hellman
d) None of the mentioned

12. Which should be used first to decrypt?
a) Public key
b) Private key
c) Public & Private key
d) None of the mentioned

13. The digital signature provides authentication to the
a) Sender
b) Message
c) Sender & Message
d) None of the mentioned

14. In hash function output length is fixed.
a) True
b) False

15. The hash function
a) Is collision free
b) Has manageable collision
c) Has high unmanageable level of collision
d) None of the mentioned

16. DSA protocol is based on
a) Discrete logarithm problem
b) Continuous logarithm problem
c) Discrete & Continuous logarithm problem
d) None of the mentioned

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