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package wildarsa;
import java.math.BigInteger;
import java.util.Random;
import java.io.*;
/**
 *
 * @author wilda
 */
public class Wildarsa { private BigInteger p;
    private BigInteger q;
    private BigInteger N;
    private BigInteger phi;
    private BigInteger e;
    private BigInteger d;
    private int bitlength = 1024;
    private int blocksize = 256; //blocksize in byte

    private Random r;
     public Wildarsa() {
        r = new Random();
        p = BigInteger.probablePrime(bitlength, r);
        q = BigInteger.probablePrime(bitlength, r);
          N = p.multiply(q);

        phi = p.subtract(BigInteger.ONE).multiply(q.subtract(BigInteger.ONE));
          e = BigInteger.probablePrime(bitlength/2, r);

        while (phi.gcd(e).compareTo(BigInteger.ONE) > 0 && e.compareTo(phi) < 0 ) {
            e.add(BigInteger.ONE);
        }
 d = e.modInverse(phi);
    }

    public Wildarsa(BigInteger e, BigInteger d, BigInteger N) {
        this.e = e;
        this.d = d;
        this.N = N;
    }


public static void main (String[] args) throws IOException
{
        Wildarsa rsa_wilda = new Wildarsa();
           DataInputStream in=new DataInputStream(System.in);
        String teststring ;
         System.out.println("Enter the plain text:");
        teststring=in.readLine();
        System.out.println("Encrypting String: " + teststring);
        System.out.println("String in Bytes: " + bytesToString(teststring.getBytes()));

        // encrypt
        byte[] encrypted = rsa_wilda.encrypt(teststring.getBytes());
        System.out.println("Encrypted String in Bytes: " + bytesToString(encrypted));

        // decrypt
        byte[] decrypted = rsa_wilda.decrypt(encrypted);
        System.out.println("Decrypted String in Bytes: " +  bytesToString(decrypted));

        System.out.println("Decrypted String: " + new String(decrypted));

    }

   private static String bytesToString(byte[] encrypted) {
        String test = "";
        for (byte b : encrypted) {
            test += Byte.toString(b);
        }
        return test;
    }

     public byte[] encrypt(byte[] message) {
        return (new BigInteger(message)).modPow(e, N).toByteArray();
    }

    public byte[] decrypt(byte[] message) {
        return (new BigInteger(message)).modPow(d, N).toByteArray();
    }

}