CNS_Lab

1. Perform encryption and decryption using mono-alphabetic cipher. The program should support the following :

    Construct an input file named plaintext.txt (consisting of 1000 alphabets, without any space or special characters)
    
    Encrypt the characters of plaintext.txt and store the corresponding ciphertext characters in   ciphertext.txt
   
    Compute the frequency of occurrence of each alphabet in both plaintext.txt and ciphertext.txt  and tabulate the results
   

2. Write a program to perform the following using Playfair cipher technique

    Encrypt a given message M with different keys {k1,k2,...,kn}.
    Print key and cipher text pair
    Decrypt the cipher texts obtained in (i) to get back M
   

3. Write a program to perform the following using Hill cipher:

    Encrypt a message M with a given key matrix of size 2X2 and 3X3
    Decrypt the cipher text obtained in (i) by computing inverse of the respective key matrix.
   

4. Write a program to perform encryption and decryption using transposition technique with column permutation given as key.

5. Generate and print 48-bit keys for all sixteen rounds of DES algorithm, given a 64-bit initial key.

6. Given 64-bit output of (i-1)th round of DES, 48-bit ith round key Ki and E table, find the 48-bit input for S-box.

7. Given 48-bit input to S-box and permutation table P, find the 32-bit output Ri of ith round of DES algorithm.

8. Write a program to generate large random number using BBS random number generator algorithm and check whether the generated number is prime or not using RABIN-MILLER primality testing algorithm