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/*
 * This file is part of Aion-Finish 
 * 
 * Aion-Finish 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-Finish 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-Finish. If not, see .
 */
package at.chrl.nutils.ncrypt;

import java.security.GeneralSecurityException;
import java.security.KeyPairGenerator;
import java.security.spec.RSAKeyGenParameterSpec;

import javax.crypto.Cipher;
import javax.crypto.KeyGenerator;
import javax.crypto.SecretKey;

import at.chrl.nutils.Rnd;

/**
 * Key generator. It generates keys or keyPairs for Blowfish and RSA
 *
 * @author -Nemesiss-
 *
 */
public class KeyGen {
	/**
	 * 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 {
		System.out.println(String.format("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)];
	}
}