Block Ciphers and the Data Encryption Standard

This is a computer science engineering quiz on cryptography and network security, which includes questions on Block Ciphers and the Data Encryption Standard.

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In affine block cipher systems if f(m)=Am + t, what is f(m1+m2) ?

f(m1) + f(m2) + t f(m1) + f(m2) + 2t f(m1) + t f(m1) + f(m2)

In affine block cipher systems if f(m)=Am + t, what is f(m1+m2+m3) ?

f(m1) + f(m2) + f(m3) + t f(m1) + f(m2) + f(m3) +2t f(m1) + f(m2) + f(m3) 2(f(m1) + f(m2) + f(m3))

If the block size is ‘s’, how many affine transformations are possible ?

2s (2s-1)(2s-1)(2s-12)………(2s-1(s-1)) 2s (2s-1)(2s-2)(2s-22)………(2s-2(s-2)) 2ss (2s-1)(2s-2)(2s-22)………(2s-2(s-1)) 2s (2s-1)(2s-2)(2s-22)………(2s-2(s-3))

What is the number of possible 3 x 3 affine cipher transformations ?

168 840 1024 1344

Super-Encipherment using two affine transformations results in another affine transformation.

True False

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

010110011 111000011 110110111 010110110

Confusion hides the relationship between the ciphertext and the plaintext.

True False

The S-Box is used to provide confusion, as it is dependent on the unknown key.

True False

In the DES algorithm, although the key size is 64 bits only 48bits are used for the encryption procedure, the rest are parity bits.

True False

In the DES algorithm the round key is __________ bit and the Round Input is ____________bits.

48, 32 64,32 56, 24 32, 32

In the DES algorithm the Round Input is 32 bits, which is expanded to 48 bits via ____________

Scaling of the existing bits Duplication of the existing bits Addition of zeros Addition of ones

The Initial Permutation table/matrix is of size: