Question

Write a Java program to encrypt the following message using the RC4 cipher using key CODES:

Cryptography is a method of protecting information and communications through the use of codes so that only those for whom the information is intended can read and process it.

Instead of using stream length 256, we will use length 26. When encrypting, let A = 0 to Z = 25 (hence CODES = [2 14 3 4 18]). Ignore spaces and punctuations and put the message in groups of five letters.

Answer 1

For the above problem, we need to have the following things into consideration.

1. We need to convert each character into a lower case in order to reduce the work to be done.
2. We need to Get the cryptic version only for the characters, not for the punctuation.

Following is the JAVA program:

import java.util.ArrayList;
import java.util.List;

public class Crypt {
   public static void main(String args[])
   {
       String message = "This is the message";
       List<Integer> crypt = new ArrayList<Integer>();
       for(int i = 0 ; i < message.length(); i++) {
           char current = Character.toLowerCase(message.charAt(i));
           if(current >= 'a' && current <= 'z') {
               crypt.add(current - 'a');
           }
       }
       System.out.print("Printing the Crypt Message: [");
       for(int i = 0 ;i<crypt.size();i++) {
           System.out.print(crypt.get(i) + " " );
       }
       System.out.println("]");
   }

}

In the above program, there is a variable message in which we need to provide the message and then crypt is the list which will store the output.
Following is the output of the above-written program:

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