Digital Communications

Pretty Good Privacy

Question 1
Marks : +2 | -2
Pass Ratio : 100%
Data compression includes
Removal of redundant character
Uniform distribution of characters
Removal of redundant character & Uniform distribution of characters
None of the mentioned
Explanation:
Data compression removes redundant character strings in a file and produces a more uniform distribution of characters.
Question 2
Marks : +2 | -2
Pass Ratio : 100%
These three ciphers can operate of ______ of plaintext and cipher text.
128 bit blocks
64 bit blocks
256 bit blocks
156 bit blocks
Explanation:
The three ciphers – Triple-DES, IDEA and CAST can operate on 64 bit blocks of plain text and cipher text.
Question 3
Marks : +2 | -2
Pass Ratio : 100%
Which operation is used in encryption using IDEA?
Addition modulo 216
Bit wise XOR
Addition modulo 216 & Bit wise XOR
None of the mentioned
Explanation:
The arithmetic operations used in IDEA are addition modulo 216, multiplication modulo 216+1, and bit wise XOR.
Question 4
Marks : +2 | -2
Pass Ratio : 100%
PGP offers _____ block ciphers for message encryption.
Triple-DES
CAST
IDEA
All of the mentioned
Explanation:
Pretty good privacy security system offers three block ciphers for message encryption – Triple-DES, IDEA and CAST.
Question 5
Marks : +2 | -2
Pass Ratio : 100%
For digital signatures private key cryptosystem is used.
True
False
Explanation:
Public key cryptosystem is used for the creation of digital signatures.
Question 6
Marks : +2 | -2
Pass Ratio : 100%
What is the key size allowed in PGP?
1024-1056
1024-4056
1024-4096
1024-2048
Explanation:
Pretty good privacy security system allows 1024 to 4096 bits of key size.
Question 7
Marks : +2 | -2
Pass Ratio : 100%
Which block cipher has key length of 128 bits?
IDEA
CAST
IDEA & CAST
None of the mentioned
Explanation:
The block ciphers IDEA and CAST has key length of 128 bits where as Triple-DES has key size of 168 bits.
Question 8
Marks : +2 | -2
Pass Ratio : 100%
Pretty good privacy (PGP) security system uses
Public key cryptosystem
Private key cryptosystem
Public & Private key cryptosystem
None of the mentioned
Explanation:
PGP uses many encryption techniques such as private key cryptosystem and also public key cryptosystem.
Question 9
Marks : +2 | -2
Pass Ratio : 100%
The key size of DES is
56 bits
64 bits
128 bits
168 bits
Explanation:
The key size of DES algorithm is 56 bits and with Triple-DES, the message to be encrypted is run on DES algorithm 3 times.
Question 10
Marks : +2 | -2
Pass Ratio : 100%
Public key cryptosystem is used for the encryption of
Messages
Session key
Session key & Messages
None of the mentioned
Explanation:
Public key cryptosystem is used for encryption of messages and private key cryptosystem is used for encryption of messages.