Friday, 9 May 2014

Java program for Mono-alphabetic Substitution Cipher

import javax.swing.JOptionPane;

/**
 *
 * @author dixit bhatta
 */
public class Monoalphabetic {
    public static String key = "ISYVKJRUXEDZQMCTPLOFNBWGAH";
    public static void main(String[] args) {
        // TODO code application logic here
        String text;
        int ch;
        ch = Integer.parseInt(JOptionPane.showInputDialog(null, "Enter 1 to Encrypt and 2 to Decrypt!"));
        text = JOptionPane.showInputDialog(null, "Enter plain/cipher text to encrypt?");
        text = text.toUpperCase();
        text = text.replaceAll("\\s",""); //removing spaces
        char[] ptextchars = text.toCharArray();
        switch(ch){
            case 1:
                    for(int i=0;i< text.length(); i++){
                        ptextchars[i] = encrypt(ptextchars[i]);
                    }
                    break;
            case 2:
                    for(int i=0;i< text.length(); i++){
                        ptextchars[i] = decrypt(ptextchars[i]);
                    }
                    break;
            default: System.out.println("Invalid Choice!");
        }
        System.out.println(ptextchars);
    }

        private static char encrypt(char a) {
            int pos = (int)a;
            pos = (pos % 91)- 65;
            a = key.charAt(pos);
            return a;
        }

        private static char decrypt(char a) {
            int ascii = 0;
            for(int i=0;i< key.length(); i++){
                if(key.charAt(i) == a)
                    ascii = i + 65;
            }
            return (char)ascii;
        }  
}

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