/**
 * <p>COMP3441/9441 Assignment 2 Example Code</p>
 * <p>Session 2, 2003</p>
 * @author Halvard Skogsrud
 */

import java.security.*;
import java.security.Security.*;
import java.security.interfaces.*;
import javax.crypto.* ;

public class Test {
  /**
   * The message we want to encrypt
   */
  public static final String CLEARTEXT = "Hello world";

  /**
   * <p>This method does the following:</p>
   * <ol>
   * <li>Adds the Cryptix provider to JCE</li>
   * <li>Generates an RSA key pair</li>
   * <li>Initializes the RSA cipher</li>
   * <li>Encrypts a string using RSA</li>
   * <li>Decrypts the encrypted string</li>
   * </ol>
   */
  public static void main (String[] args) {
	try {
	  // add our open-source provider, which can do RSA encryption
	  Security.addProvider(new cryptix.jce.provider.CryptixCrypto());
	  // just print some information on the crypto provider package
	  Provider cryptix = Security.getProvider("CryptixCrypto");
	  System.out.println(cryptix.getName() + " " + cryptix.getVersion());
	  System.out.println(cryptix.getInfo());
	  
	  // create an RSA key pair generator object
	  KeyPairGenerator gen = KeyPairGenerator.getInstance("RSA");
	  // set the key size to the desired number of bits (max 2048)
	  gen.initialize(512);
	  // generate the RSA key pair
	  KeyPair pair = gen.generateKeyPair();

	  // extract the public and private keys
	  RSAPublicKey publicKey = (RSAPublicKey) pair.getPublic();
	  RSAPrivateKey privateKey = (RSAPrivateKey) pair.getPrivate();

	  // initialize the RSA cipher in ECB mode
	  Cipher c = Cipher.getInstance("RSA/ECB/PKCS#1");
	  // set the cipher to do encryption
	  c.init(Cipher.ENCRYPT_MODE, publicKey);
	  // encrypt the sample string
	  byte[] ciphertext = c.doFinal(CLEARTEXT.getBytes());

	  // set the cipher to do decryption
	  c.init(Cipher.DECRYPT_MODE, privateKey);
	  // decrypt the encrypted sample string
	  byte[] decryptedText = c.doFinal(ciphertext);

	  // print out the strings
	  System.out.println("Original string:  " + CLEARTEXT);
	  System.out.println("Encrypted string: " + new String(ciphertext));
	  System.out.println("Decrypted string: " + new String(decryptedText));
	} 
	catch (Throwable t) {
	  t.printStackTrace();
	}
  }
}