Question

1. We have learned a famous shift cipher called Caesar Cipher. Now if we are given a plain test: THE ART OF WARAnd key = 3 (a shift by 3 letters), please give the ciphertext

2. Given an 8 bit block P = 10101111 and a key K = 01101011, please give the result of bitwise XOR between P and K

3. Please give the left 2 shift of the 8 bit text 01100101

4. Use the given a permutation table 23614857 to define a new 8 bit from an 8 bit text 10100110

5. Define a substitution box, So as following table

1	0	3	2
3	2	1	0
0	2	1	3
1	1	3	2

and a substitution scheme that if we denote a 4 bit number as “b1 b2 b3 b4”, the (b1 b4) forms a 2 bit binary number that specifies a row of the above matrix and the (b2 b3) forms another 2 bit binary number that specifies a column of the matrix. The row and column lead to a number in the matrix. Taking the number and translating it into binary, we get the substitution value for the original 4 bit number. Now given a 4 bit 1001, please give the substitute value.

Define a Nib Table as follows

nib	S−box(nib)		nib	S−box(nib)
0000	1001		1000	0110
0001	0100		1001	0010
0010	1010		1010	0000
0011	1011		1011	0011
0100	1101		1100	1100
0101	0001		1101	1110
0110	1000		1110	1111
0111	0101		1111	0111

What is SubNib(1010 0101)?

Answer 1

a)

THE ART OF WAR, key=3

Shift all character by 3

like A to D, B to E.... X to A, Y to B and Z to C

Answer = WKH DUW RI ZDU

T->W, H-> K and so on

b)

P = 10101111

K = 01101011

XOR = 11000100 (same bit gives 0 and different give 1)

c)

left 2 shift of the 8 bit text 01100101

Aswer = 100101 00 (trim first 2 bits and add 2 0s in end)

d)

1	0	3	2
3	2	1	0
0	2	1	3
1	1	3	2

number = 1001, b1=1, b2=0, b3=0, b4=1

11 for row (b1b4)

00 for column (b2b3)

3rd row and 0th column = 1 (0001 in binary)