Stream Encryption and Commercial Applications

Question 1
Marks : +2 | -2
Pass Ratio : 100%
In which method cipher feedback is used?
Synchronous encryption method
Self synchronous encryption method
All of the mentioned
None of the mentioned
Explanation:
In self synchronous encryption technique, cipher feedback is used and the key-stream is related to the messages.
Question 2
Marks : +2 | -2
Pass Ratio : 100%
In substitution technique encryption protection is more.
True
False
Explanation:
The substitution techniques have less encryption protection.
Question 3
Marks : +2 | -2
Pass Ratio : 100%
Spread spectrum multiple access techniques allows the multiple signal to be transmitted
One after the other
Simultaneously
All of the mentioned
None of the mentioned
Explanation:
Spread spectrum multiple access technique allows multiple signals occupying the same RF bandwidth to be transmitted simultaneously without interfering with one and another.
Question 4
Marks : +2 | -2
Pass Ratio : 100%
One-time pad has
Random key
Unconditional security
Can be used only once
All of the mentioned
Explanation:
One time pad is an encryption system with random key, used one time only, that exhibits unconditional security.
Question 5
Marks : +2 | -2
Pass Ratio : 100%
The segment of the key-stream of plaintext is obtained by _____ of two sequences together.
ANDing
ORing
Addition
Modulo 2 addition
Explanation:
The crypt-analyst performs modulo 2 addition of two sequences together to get the sequence of key-stream of plaintext.
Question 6
Marks : +2 | -2
Pass Ratio : 100%
In which method the key-stream is generated independently of the message?
Synchronous encryption method
Self synchronous encryption method
All of the mentioned
None of the mentioned
Explanation:
In Synchronous encryption method, the key-stream is generated independently of message.
Question 7
Marks : +2 | -2
Pass Ratio : 100%
Which are called as substitution encryption techniques?
Caesar cipher
Trithemius cipher
Caesar & Trithemius cipher
None of the mentioned
Explanation:
Examples of substitution encryption techniques are Caesar cipher and Trithemius cipher.
Question 8
Marks : +2 | -2
Pass Ratio : 100%
The 64 bit block input key has _____ number of parity bits.
4
6
8
16
Explanation:
The 64 bit input key has 8 parity bits placed in 8,16…..64 bit positions.
Question 9
Marks : +2 | -2
Pass Ratio : 100%
Perfect secrecy can be achieved for
Finite number of messages
Infinite number of messages
Finite & Infinite number of messages
None of the mentioned
Explanation:
Perfect secrecy can be achieved for infinite number of messages since each message would be encrypted with different portion of random key.
Question 10
Marks : +2 | -2
Pass Ratio : 100%
The standard building block uses _______ of a key to transform 64-bit input into 64-bit output.
32 bit
48 bit
64 bit
128 bit
Explanation:
The standard building block uses 48 bit keys to transform 64 bit input data into 64 bit output.