1. If the key is 110100001, the output of the SP network for the plaintext: 101110001 is
a) 110100011
b) 110101110
c) 010110111
d) 011111010
Explanation:
2. If the key is 110100001 where,
If ki=0, then S_i (x)=((1 1 0 | 0 1 1 | 1 0 0 ))x+((1 1 1))
and If ki=1, then S_i (x)=((0 1 1 | 1 0 1 | 1 0 0))x+((0 1 1))
then the output of the SP network for the plaintext: 101110001 is
a) 010110011
b) 111000011
c) 110110111
d) 010110110
Explanation:
3. Confusion hides the relationship between the ciphertext and the plaintext.
a) True
b) False
Explanation: Confusion hides the relationship between the ciphertext and the key.
4. The S-Box is used to provide confusion, as it is dependent on the unknown key.
a) True
b) False
Explanation: The S-Box is used to provide confusion, as it is dependent on the unknown key.
The P-Box is fixed, and there is no confusion due to it, but it provides diffusion.
5. 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
a) 1 and 3
b) 2 and 3
c) 3 and 4
d) 2 and 4
Explanation: Increase in any of the above 4 leads to slowing of the cipher algorithm i.e. more computational time will be required.
6. DES follows
a) Hash Algorithm
b) Caesars Cipher
c) Feistel Cipher Structure
d) SP Networks
Explanation: DES follows Feistel Cipher Structure.
7. The DES Algorithm Cipher System consists of ____________rounds (iterations) each with a round key
a) 12
b) 18
c) 9
d) 16
Explanation: The DES Algorithm Cipher System consists of 16 rounds (iterations) each with a round key.
8. The DES algorithm has a key length of
a) 128 Bits
b) 32 Bits
c) 64 Bits
d) 16 Bits
Explanation: DES encrypts blocks of 64 bits using a 64 bit key.
9. In the DES algorithm, although the key size is 64 bits only 48bits are used for the encryption procedure, the rest are parity bits.
a) True
b) False
Explanation: 56 bits are used, the rest 8 bits are parity bits.
10. In the DES algorithm the round key is __________ bit and the Round Input is ____________bits.
a) 48, 32
b) 64,32
c) 56, 24
d) 32, 32
Explanation: The round key is 48 bits. The input is 32 bits.