Question:
Below is given a cipher text encrypted in two steps, the first step is that it is enciphered by using the method of hill cipher, there the Key Matrix used is 
M  = [17  21;  8  13]. 
The alphabet is English and the length is 26, English. 

The second step is transposition, where two rows are firstly concatenated and then the cipher text line is rearranged by using a second keyword, the keyword is ‘water’ which is used consecutively until the end. 

Ciher text is in file CT.txt. 

Question 1- Find the matrix to decrypt the message. 
Question 2- a) Reverse the transposition; b) and then decipher the reverse transpositioned cipher text to obtain the plain text. 
Question 3-Write a program to decipher the image. 
Question 4-Write a program to encipher the image. 

Marks for each question is 25.

Programming Matlab or  c program and executables must be submitted. 

To be submitted by email. 
Due date: 6/April/10.