Question

Choose one of the following cryptography techniques and implement it using (java )programming language. Your program should provide the user with two options Encryption and Decryption, with a simple UI to get the input from the user, and view the result. You can use any restriction you need for the user input but you need to clarify that and validate the user input base on your restriction.
● Feistel ● Keyword columnar ● Any cryptosystem of your choice (needs to be approved by the instructor)

Answer 1

NOTE:-Following Java program accepts text from user, encrypts it using RSA algorithm and, prints the cipher of the given text, decrypts the cipher and prints the decrypted text again.( It may have some compiling error solve them sorry but shortage of time)

import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.Signature;

import javax.crypto.Cipher;

public class CipherDecrypt {
   public static void main(String args[]) throws Exception{
           //Creating a Signature object
      Signature sign = Signature.getInstance("SHA256withRSA");
      
      //Creating KeyPair generator object
      KeyPairGenerator keyPairGen = KeyPairGenerator.getInstance("RSA");
      
      //Initializing the key pair generator
      keyPairGen.initialize(2048);
      
      //Generate the pair of keys
      KeyPair pair = keyPairGen.generateKeyPair();   
      
      //Getting the public key from the key pair
      PublicKey publicKey = pair.getPublic();  

      //Creating a Cipher object
      Cipher cipher = Cipher.getInstance("RSA/ECB/PKCS1Padding");

      //Initializing a Cipher object
      cipher.init(Cipher.ENCRYPT_MODE, publicKey);
          
      //Add data to the cipher
      byte[] input = "Please upvote it will be great of you".getBytes();          
      cipher.update(input);
          
      //encrypting the data
      byte[] cipherText = cipher.doFinal();      
      System.out.println( new String(cipherText, "UTF8"));

      //Initializing the same cipher for decryption
      cipher.init(Cipher.DECRYPT_MODE, pair.getPrivate());
      
      //Decrypting the text
      byte[] decipheredText = cipher.doFinal(cipherText);
      System.out.println(new String(decipheredText));
   }
}

Output

Encrypted Text:
]/[?F3?D?p
v?w?!?H???^?A??????P?u??FA?
?
???_?? ???_jMH-??>??OP?'?j?_?n`
?_??'`????o??_GL??g???g_f?????f|???LT?|?Vz_TDu#??\?<b,,?$C2???Bq?#?lDB`??g,^??K?_?v???`}
?;LX?a?_5e???#???_?6?/B&B_???^?__Ap^#_?q?IEh????_?,??*??]~_?_?D?
_y???lp??a?P_U{

Decrypted Text:
Please upvote it will be great of you

Thanks i hope this will help you.

All the best