Cryptography and Network Security Lab ( PART A PROGRAMS )

This repository contains programs of Part A implemented in Cryptography and network security Lab in my 7th semester of SIT(VTU).

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. Implement the following with respect to RC4:

   • Print first n key bytes generated by key generation process.
   • Illustrate encryption/decryption by accepting one byte data as input on the above generated keys.