Digital Communications

Public Key Cryptosystems

Question 1
Marks : +2 | -2
Pass Ratio : 100%
Cipher system can be solved effectively by statistically using
Time of occurrence
Frequency of occurrence
Length of the message
None of the mentioned
Explanation:
By statistically using the frequency of occurrence of individual characters and character combinations we can solve many cipher systems.
Question 2
Marks : +2 | -2
Pass Ratio : 100%
The substitution of the letters are done
Serially
Parallel way
Serially & Parallel way
None of the mentioned
Explanation:
The substitution part of the encryption scheme is performed in parallel on small segment of the blocks.
Question 3
Marks : +2 | -2
Pass Ratio : 100%
Which algorithm can be used to sign a message?
Public key algorithm
Private key algorithm
Public & Private key algorithm
None of the mentioned
Explanation:
Public key algorithms are used to sign a message and private key algorithms are used to encrypt the messages.
Question 4
Marks : +2 | -2
Pass Ratio : 100%
In public key cryptosystem which is kept as public?
Encryption keys
Decryption keys
Encryption & Decryption keys
None of the mentioned
Explanation:
In public key cryptosystem, the encryption keys are kept as public where as decryption keys are kept as secret.
Question 5
Marks : +2 | -2
Pass Ratio : 100%
Which are called the block ciphers?
IDEA
CAST
Triple-DES
All of the mentioned
Explanation:
Some of the examples of block codes are triple-DES, CAST and IDEA.
Question 6
Marks : +2 | -2
Pass Ratio : 100%
In a trapdoor function, the functions are easy to go in
One direction
Two directions
All directions
None of the mentioned
Explanation:
A trapdoor is a one way function. Such functions can go easily in only one direction.
Question 7
Marks : +2 | -2
Pass Ratio : 100%
Examples of hash functions are
MD5
SHA-1
MD5 & SHA-1
None of the mentioned
Explanation:
Some examples of hash functions are MD5 and SHA-1.
Question 8
Marks : +2 | -2
Pass Ratio : 100%
Encryption transformations are known as
Diffusion
Confusion
Diffusion & Confusion
None of the mentioned
Explanation:
The encryption transformations were termed confusion and diffusion by Shannon.
Question 9
Marks : +2 | -2
Pass Ratio : 100%
PGP system uses
Private key system
Public key system
Private & Public key system
None of the mentioned
Explanation:
Pretty good privacy system uses both private key and public key based systems.
Question 10
Marks : +2 | -2
Pass Ratio : 100%
In which method, key-stream is generated independently?
Synchronous
Self synchronous
Synchronous & Self synchronous
None of the mentioned
Explanation:
In synchronous encryption system, the key-stream is generated independently of the message.