/**
 * myRSA.java
 *
 * A simple implementation of the RSA algorithm.
 *
 * Example usage:
 *
 *   myRSA rsa = new myRSA(100);
 *   rsa.setPublicKey(1,2);
 *   rsa.setPrivateExponent(3);
 *   rsa.encode();
 *   BigInteger result = rsa.getResult();
 *   System.out.println('The encoded value is: ' + result);
 *   rsa.decode();
 *   BigInteger result2 = rsa.getResult();
 *   System.out.println('The decoded value is: ' + result2);
 *
 * @see http://www.rsasecurity.com/rsalabs/node.asp?id=2125
 * @author Nubsauce <nubsauce@nubnub.com>
 */ 

import java.lang.Object;
import java.math.BigInteger;

public class myRSA
{
    /**
     * The public key.
     * @var integer
     */
    private int publicKey;
    
    /**
     * The second part of the public key.
     * @var integer
     */
    private int keyPart;
    
    /**
     * The private exponent.
     * @var integer
     */
    private int pExponent;
    
    /**
     * The value that is to be encoded/decoded.
     * @var integer
     */
    private BigInteger rsaValue;    
     
    /**
     * Constructor for objects of class ownversion.
     * Sets the value that is to be encoded/decoded.
     *
     * @param integer x The value that is to be manipulated.
     * @return void
     */
    public myRSA(int x)
    {
        rsaValue = x;
    }

    /**
     * Sets the public key.
     *
     * @param integer firstPart The first part of the public key.
     * @param integer secondPart The Second part of the public key.
     * @return void
     */
    public void setPublicKey(int firstPart, int secondPart)
    {
        publicKey = firstPart;
        keyPart   = secondPart;
    }

    /**
     * Sets the private exponent.
     * @param integer exp The private exponent.
     * @return void
     */
    public void setPrivateExponent(int exp)
    {
        pExponent = exp;
    }
    
    /**
     * Encodes the stored value using an RSA algorithm.
     *
     * @return void
     */
    public void encode()
    {
        BigInteger y = BigInteger.valueOf(rsaValue);
        BigInteger e1 = BigInteger.valueOf(keyPart);
        BigInteger publicKey1 = BigInteger.valueOf(publicKey);
        BigInteger result = y.modPow(e1, publicKey1);
        rsaValue = result;
    }
    
    /**
     * Decodes the stored value using an RSA algorithm.
     *
     * @return void
     */
    public void decode()
    {
        BigInteger z1 = BigInteger.valueOf(rsaValue);
        BigInteger d1 = BigInteger.valueOf(privateExponent);
        BigInteger publicKey1 = BigInteger.valueOf(publicKey);
        BigInteger result = z1.modPow(d1, publickey1);
        rsaValue = result;
    }
    
    /**
     * Returns the processed value.
     *
     * @return integer
     */
    public BigInteger getResult()
    {
        return rsaValue;
    }
}