package ly.util;

import javax.crypto.Cipher;

import sun.security.provider.Sun;

import java.security.*;
import java.security.spec.RSAPublicKeySpec;
import java.security.spec.RSAPrivateKeySpec;
import java.security.spec.InvalidKeySpecException;
import java.security.interfaces.RSAPrivateKey;
import java.security.interfaces.RSAPublicKey;
import java.io.*;
import java.math.BigInteger;

/**
 * RSA 工具類。提供加密，解密，生成密鑰對等方法。
 * 
 */
public class lyRSA {

	/**
	 * 生成密鑰對
	 * 
	 * @return KeyPair
	 * @throws EncryptException
	 */
	public static KeyPair generateKeyPair(int key_size) throws EncryptException {
		try {
			KeyPairGenerator keyPairGen = KeyPairGenerator.getInstance("RSA",new org.bouncycastle.jce.provider.BouncyCastleProvider());
			//KeyPairGenerator keyPairGen = KeyPairGenerator.getInstance("RSA",new Sun());
			final int KEY_SIZE = key_size;// Key長度 默認使用1024
			keyPairGen.initialize(KEY_SIZE, new SecureRandom());
			KeyPair keyPair = keyPairGen.genKeyPair();
			return keyPair;
		} catch (Exception e) {
			throw new EncryptException(e.getMessage());
		}
	}

	/**
	 * 生成公鑰
	 * 
	 * @param modulus
	 * @param publicExponent
	 * @return RSAPublicKey
	 * @throws EncryptException
	 */
	public static RSAPublicKey generateRSAPublicKey(byte[] modulus,
			byte[] publicExponent) throws EncryptException {
		KeyFactory keyFac = null;
		try {
			keyFac = KeyFactory.getInstance("RSA",new org.bouncycastle.jce.provider.BouncyCastleProvider());
			//keyFac = KeyFactory.getInstance("RSA",new Sun());
		} catch (NoSuchAlgorithmException ex) {
			throw new EncryptException(ex.getMessage());
		}

		RSAPublicKeySpec pubKeySpec = new RSAPublicKeySpec(new BigInteger(
				modulus), new BigInteger(publicExponent));
		try {
			return (RSAPublicKey) keyFac.generatePublic(pubKeySpec);
		} catch (InvalidKeySpecException ex) {
			throw new EncryptException(ex.getMessage());
		}
	}

	/**
	 * 生成私鑰
	 * 
	 * @param modulus
	 * @param privateExponent
	 * @return RSAPrivateKey
	 * @throws EncryptException
	 */
	public static RSAPrivateKey generateRSAPrivateKey(byte[] modulus,
			byte[] privateExponent) throws EncryptException {
		KeyFactory keyFac = null;
		try {
			keyFac = KeyFactory.getInstance("RSA",new org.bouncycastle.jce.provider.BouncyCastleProvider());
			//keyFac = KeyFactory.getInstance("RSA",new Sun());
		} catch (NoSuchAlgorithmException ex) {
			throw new EncryptException(ex.getMessage());
		}

		RSAPrivateKeySpec priKeySpec = new RSAPrivateKeySpec(new BigInteger(
				modulus), new BigInteger(privateExponent));
		try {
			return (RSAPrivateKey) keyFac.generatePrivate(priKeySpec);
		} catch (InvalidKeySpecException ex) {
			throw new EncryptException(ex.getMessage());
		}
	}

	/**
	 * 加密
	 * 
	 * @param key
	 *            加密的密鑰
	 * @param data
	 *            待加密的明文數據
	 * @return 加密后的數據
	 * @throws EncryptException
	 */
	public static byte[] encrypt(Key key, byte[] data) throws EncryptException {
		try {
			Cipher cipher = Cipher.getInstance("RSA",new org.bouncycastle.jce.provider.BouncyCastleProvider());
			//Cipher cipher = Cipher.getInstance("RSA",new Sun());
			cipher.init(Cipher.ENCRYPT_MODE, key);
			int blockSize = cipher.getBlockSize();// 獲得加密塊大小，如：加密前數據為128個byte，而key_size=1024
													// 加密塊大小為127
													// byte,加密后為128個byte;因此共有2個加密塊，第一個127
													// byte第二個為1個byte
			int outputSize = cipher.getOutputSize(data.length);// 獲得加密塊加密后塊大小
			int leavedSize = data.length % blockSize;
			int blocksSize = leavedSize != 0 ? data.length / blockSize + 1
					: data.length / blockSize;
			byte[] raw = new byte[outputSize * blocksSize];
			int i = 0;
			while (data.length - i * blockSize > 0) {
				if (data.length - i * blockSize > blockSize)
					cipher.doFinal(data, i * blockSize, blockSize, raw, i
							* outputSize);
				else
					cipher.doFinal(data, i * blockSize, data.length - i
							* blockSize, raw, i * outputSize);
				// 這里面doUpdate方法不可用，查看源代碼后發現每次doUpdate后并沒有什么實際動作除了把byte[]放到ByteArrayOutputStream中，而最后doFinal的時候才將所有的byte[]進行加密，可是到了此時加密塊大小很可能已經超出了OutputSize所以只好用dofinal方法。

				i++;
			}
			return raw;
		} catch (Exception e) {
			throw new EncryptException(e.getMessage());
		}
	}

	/**
	 * 解密
	 * 
	 * @param key
	 *            解密的密鑰
	 * @param raw
	 *            已經加密的數據
	 * @return 解密后的明文
	 * @throws EncryptException
	 */
	public static byte[] decrypt(Key key, byte[] raw) throws EncryptException {
		try {
			Cipher cipher = Cipher.getInstance("RSA",new org.bouncycastle.jce.provider.BouncyCastleProvider());
			//Cipher cipher = Cipher.getInstance("RSA",new Sun());
			cipher.init(cipher.DECRYPT_MODE, key);
			int blockSize = cipher.getBlockSize();
			ByteArrayOutputStream bout = new ByteArrayOutputStream(64);
			int j = 0;

			while (raw.length - j * blockSize > 0) {
				bout.write(cipher.doFinal(raw, j * blockSize, blockSize));
				j++;
			}
			return bout.toByteArray();
		} catch (Exception e) {
			throw new EncryptException(e.getMessage());
		}
	}
/*
 
	public static void main(String[] args) throws Exception {
		File file = new File("test.html");
		FileInputStream in = new FileInputStream(file);
		ByteArrayOutputStream bout = new ByteArrayOutputStream();
		byte[] tmpbuf = new byte[1024];
		int count = 0;
		while ((count = in.read(tmpbuf)) != -1) {
			bout.write(tmpbuf, 0, count);
			tmpbuf = new byte[1024];
		}
		in.close();
		byte[] orgData = bout.toByteArray();
		
		KeyPair keyPair = lyRSA.generateKeyPair(1024);
		RSAPublicKey pubKey = (RSAPublicKey) keyPair.getPublic();
		RSAPrivateKey priKey = (RSAPrivateKey) keyPair.getPrivate();

		byte[] pubModBytes = pubKey.getModulus().toByteArray();//取得公要模
		byte[] pubPubExpBytes = pubKey.getPublicExponent().toByteArray();//取得公要指數
		byte[] priModBytes = priKey.getModulus().toByteArray();//取得私要模
		byte[] priPriExpBytes = priKey.getPrivateExponent().toByteArray();//取得私要指數
		RSAPublicKey recoveryPubKey = lyRSA.generateRSAPublicKey(pubModBytes,
				pubPubExpBytes);
		RSAPrivateKey recoveryPriKey = lyRSA.generateRSAPrivateKey(priModBytes,
				priPriExpBytes);

		byte[] raw = lyRSA.encrypt(priKey, orgData);
		file = new File("encrypt_result.dat");
		OutputStream out = new FileOutputStream(file);
		out.write(raw);
		out.close();
		byte[] data = lyRSA.decrypt(recoveryPubKey, raw);
		file = new File("decrypt_result.html");
		out = new FileOutputStream(file);
		out.write(data);
		out.flush();
		out.close();
	}
* 
*/
}