Consider the table in Figure 2.6 showing the relative frequencies of letters in English. Arrange the frequencies from largest to smallest, and make a cumulative plot, using Excel for example. Which...

Ques 1 a) figure not provided
Ques 1 b)
(i) ? and ? values for the Caeser Cipher will be ? will be a variable 1. ? will be the constant value
that will be added to the plaintext for encrypting the text and subtracted in order to decrypt the
text.
(ii) MOUNTPANORAMA encryption
? = 11
? = 7
a b c d e f g h i j k l m n o p q r s t u v w x y z
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
M = (11 * 12 + 7) mod 26 = 9 = J
O = (14 * 12 + 7) mod 26 = 5 = F
U = (20 * 12 + 7) mod 26 = 19 = T
Similarly rest of the alphabets are converted and final encrypted text is = JFTUIQHUFMHJH
(iii)
The reason for ? = 2 and ? = 0 being not good because the values might lead to same encrypted
output for different alphabets like A and N.
A = (0 * 2 + 0) mod 26 = 0 = A
N = (13 * 2 + 0) mod 26 = 0 = A
Hence not good to have this configuration.
Ques 1 c)
Suppose following is the WORDS as the sample for the Caeser Cipher Code:
ELEMENTARY CRYPTOGRAPHY FOR THE CLASS
Encrypted text: XPXZXJRJXP8DXPDRTRXJDBP8HTX8RBX8DPJHH
Randomly chosen ? and ? values for encryption.
Now let’s see the encrypted text with most number of occurrences:
X = 8 times
R = 4 Times
Let’s assume X = 3 and R as T as these alphabets have the highest frequency in the English.
Hence,
a b c d e f g h i j k l m n o p q r s t u v w x y z
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
y = E(x) = (ax+b)MOD26
Then we can “solve for x in terms of y” and so determine E−1(y).
As y (encrypted text) = (ax+b)MOD26
ax = (y-b) Mod 26
dividing by 1/a both the sides we get:
x(plaintext) = ((y-b)Mod26)/a
For E:
E(4)=(23-b)Mod26/a
Similary for T:
T(19) = (17-b)Mod26/a
Solving the Equation we get a= 10 and b as 9.
Checking: (4*10 + 9)mod 26 = X
(19*10+9)mod26 = (17) T
Ques 2)
a)
(i)
Key size of the DES = 56 bits
Hence key size would be 256 = 72057594037927936
In terms of power of 10,
10x = 72057594037927936
x log 10 = log (72057594037927936)
x * 1 =...