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WorksheetsUNIT 2 DES,BLOCK CIPHER
Total questions: 20
Worksheet time: 11mins
Which of the following is a mode of operation for the Block ciphers in cryptography?
Electronic Code Book (ECB)
Cipher Block Chaining (CBC)
Counter (CTR) mode
All of the above
For which of the following should EBC (Electronic Code Book) process not be used for encryption?
For large block sizes
For fixed block sizes
For small block sizes
none of the above
Which of the following options is not correct according to the definition of the Cipher Block Chaining (CBC)?
CBC is a mode of operation for stream ciphers.
Initialization vector (IV) is used in CBC in the initial phase.
It has better resistive nature towards cryptanalysis than ECB
None of the above
Which of the following modes of operations can be followed for both stream ciphers as well as block ciphers?
CBC
ECB
CFB
ALL THE ABOVE
Data Encryption Standard (DES) is a __________.
Stream Cipher
Bit Cipher
Block Cipher
Substitution Cipher
The S-Box is used to provide confusion, as it is dependent on the unknown key.
true
false
This is an example of
SP Networks
Feistel Cipher
Hash Algorithm
Hill Cipher
Which of the following slows the cryptographic algorithm –
1) Increase in Number of rounds
2) Decrease in Block size
3) Decrease in Key Size
4) Increase in Sub key Generation
1 and 3
2 and 3
3 and 4
2 and 4
During decryption, we use the Inverse Initial Permutation (IP-1) before the IP.
true
false
A preferable cryptographic algorithm should have a good avalanche effect.
true
false
A preferable cryptographic algorithm should have a good avalanche effect.
2^56
2^43
2^55
2^47
Using Linear Crypt-analysis, the minimum computations required to decipher the DES algorithm is
2^48
2^43
2^56
2^64
The DES Algorithm Cipher System consists of (a) rounds (iterations) each with a round key
The DES algorithm has a key length of
128 bits
32 bits
64 bits
16 bits
In the DES algorithm the round key is __________ bit and the Round Input is ____________bits.
48, 32
64,32
56,24
32,32
The Initial Permutation table/matrix is of size
16x8
12x8
8x8
4x8
In the DES algorithm the 64 bit key input is shortened to 56 bits by ignoring every 4th bit.
true
false
Euclid’s algorithm is used for finding __________
GCD of 2 nos.
GCD of more than 3 nos.
LCM of 2 nos.
LCM of more than 2 nos.
If 4 is the GCD of 16 and 12, What is the GCD of 12 and 4?
12
6
4
2
What is the formula for Euclidean algorithm?
GCD (m,n) = GCD (n, m mod n)
GCD(m,n,o,p) = GCD (m, m mod n, o, p mod o)
LCM (m,n,o,p) = LCM (m, m mod n, o, p mod o)
