/**
 * This file is part of aion-emu <aion-emu.com>.
 *
 *  aion-emu is free software: you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation, either version 3 of the License, or
 *  (at your option) any later version.
 *
 *  aion-emu is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with aion-emu.  If not, see <http://www.gnu.org/licenses/>.
 */

package com.aionemu.loginserver.network.ncrypt;

import com.aionemu.commons.utils.Rnd;
import org.apache.log4j.Logger;

import javax.crypto.Cipher;
import javax.crypto.KeyGenerator;
import javax.crypto.SecretKey;
import java.security.GeneralSecurityException;
import java.security.KeyPairGenerator;
import java.security.spec.RSAKeyGenParameterSpec;

/**
 * Key generator. It generates keys or keyPairs for Blowfish and RSA
 *
 * @author -Nemesiss-
 *
 */
public class KeyGen
{
	/**
	 * Logger for this class.
	 */
	protected static final Logger	log = Logger.getLogger(KeyGen.class);

	/**
	 * Key generator for blowfish
	 */
	private static KeyGenerator		blowfishKeyGen;

	/**
	 *  Public/Static RSA KeyPairs with encrypted modulus N
	 */
	private static EncryptedRSAKeyPair[] encryptedRSAKeyPairs;

    /**
	 * Initialize Key Generator (Blowfish keygen and RSA keygen)
	 *
	 * @throws GeneralSecurityException
	 */
	public static void init() throws GeneralSecurityException
	{
		log.info("Initializing Key Generator...");

		blowfishKeyGen = KeyGenerator.getInstance("Blowfish");

		KeyPairGenerator		rsaKeyPairGenerator = KeyPairGenerator.getInstance("RSA");

		RSAKeyGenParameterSpec	spec                = new RSAKeyGenParameterSpec(1024, RSAKeyGenParameterSpec.F4);

		rsaKeyPairGenerator.initialize(spec);

		encryptedRSAKeyPairs = new EncryptedRSAKeyPair[10];

		for(int i = 0; i < 10; i++)
		{
			encryptedRSAKeyPairs[i] = new EncryptedRSAKeyPair(rsaKeyPairGenerator.generateKeyPair());
		}

		// Pre-init RSA cipher.. saving about 300ms
		Cipher	rsaCipher = Cipher.getInstance("RSA/ECB/nopadding");

		rsaCipher.init(Cipher.DECRYPT_MODE, encryptedRSAKeyPairs[0].getRSAKeyPair().getPrivate());
	}

	/**
	 * Generate and return blowfish key
	 *
	 * @return Random generated blowfish key
	 */
	public static SecretKey generateBlowfishKey()
	{
		return blowfishKeyGen.generateKey();
	}

	/**
	 * Get common RSA Public/Static Key Pair with encrypted modulus N
	 * @return encryptedRSAkeypairs
	 */
	public static EncryptedRSAKeyPair getEncryptedRSAKeyPair()
	{
		return encryptedRSAKeyPairs[Rnd.nextInt(10)];
	}
}