import java.io.ByteArrayOutputStream;
import java.security.Key;
import java.security.KeyFactory;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.Signature;
import java.security.interfaces.RSAPrivateKey;
import java.security.interfaces.RSAPublicKey;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;
import java.util.HashMap;
import java.util.Map;

import javax.crypto.Cipher;


/**
 * <p>
 * RSA公鑰/私鑰/簽名工具包
 * </p>
 * <p>
 * 羅納德·李維斯特（Ron [R]ivest）、阿迪·薩莫爾（Adi [S]hamir）和倫納德·阿德曼（Leonard [A]dleman）
 * </p>
 * <p>
 * 字符串格式的密鑰在未在特殊說明情況下都為BASE64編碼格式<br/>
 * 由于非對稱加密速度極其緩慢，一般文件不使用它來加密而是使用對稱加密，<br/>
 * 非對稱加密算法可以用來對對稱加密的密鑰加密，這樣保證密鑰的安全也就保證了數據的安全
 * </p>
 *
 * @author IceWee
 * @version 1.0
 * @date 2012-4-26
 */
public class RSAUtils {

  /**
   * 加密算法RSA
   */
  public static final String KEY_ALGORITHM = "RSA";

  /**
   * 簽名算法
   */
  public static final String SIGNATURE_ALGORITHM = "MD5withRSA";

  /**
   * 獲取公鑰的key
   */
  private static final String PUBLIC_KEY = "RSAPublicKey";

  /**
   * 獲取私鑰的key
   */
  private static final String PRIVATE_KEY = "RSAPrivateKey";

  /**
   * RSA最大加密明文大小
   */
  private static final int MAX_ENCRYPT_BLOCK = 117;

  /**
   * RSA最大解密密文大小
   */
  private static final int MAX_DECRYPT_BLOCK = 128;

  /**
   * <p>
   * 生成密鑰對(公鑰和私鑰)
   * </p>
   *
   * @return
   * @throws Exception
   */
  public static Map<String, Object> genKeyPair() throws Exception {
    KeyPairGenerator keyPairGen = KeyPairGenerator.getInstance(KEY_ALGORITHM);
    keyPairGen.initialize(1024);
    KeyPair keyPair = keyPairGen.generateKeyPair();
    RSAPublicKey publicKey = (RSAPublicKey) keyPair.getPublic();
    RSAPrivateKey privateKey = (RSAPrivateKey) keyPair.getPrivate();
    Map<String, Object> keyMap = new HashMap<String, Object>(2);
    keyMap.put(PUBLIC_KEY, publicKey);
    keyMap.put(PRIVATE_KEY, privateKey);
    return keyMap;
  }

  /**
   * <p>
   * 用私鑰對信息生成數字簽名
   * </p>
   *
   * @param data    已加密數據
   * @param privateKey 私鑰(BASE64編碼)
   * @return
   * @throws Exception
   */
  public static String sign(byte[] data, String privateKey) throws Exception {
    byte[] keyBytes = Base64Utils.decode(privateKey);
    PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(keyBytes);
    KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
    PrivateKey privateK = keyFactory.generatePrivate(pkcs8KeySpec);
    Signature signature = Signature.getInstance(SIGNATURE_ALGORITHM);
    signature.initSign(privateK);
    signature.update(data);
    return Base64Utils.encode(signature.sign());
  }

  /**
   * <p>
   * 校驗數字簽名
   *
   * </p>
   *
   * @param data   已加密數據
   * @param publicKey 公鑰(BASE64編碼)
   * @param sign   數字簽名
   * @return
   * @throws Exception
   */
  public static boolean verify(byte[] data, String publicKey, String sign)
      throws Exception {
    byte[] keyBytes = Base64Utils.decode(publicKey);
    X509EncodedKeySpec keySpec = new X509EncodedKeySpec(keyBytes);
    KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
    PublicKey publicK = keyFactory.generatePublic(keySpec);
    Signature signature = Signature.getInstance(SIGNATURE_ALGORITHM);
    signature.initVerify(publicK);
    signature.update(data);
    return signature.verify(Base64Utils.decode(sign));
  }

  /**
   * <P>
   * 私鑰解密
   * </p>
   *
   * @param encryptedData 已加密數據
   * @param privateKey  私鑰(BASE64編碼)
   * @return
   * @throws Exception
   */
  public static byte[] decryptByPrivateKey(byte[] encryptedData, String privateKey)
      throws Exception {
    byte[] keyBytes = Base64Utils.decode(privateKey);
    PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(keyBytes);
    KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
    Key privateK = keyFactory.generatePrivate(pkcs8KeySpec);
//    Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
    Cipher cipher = Cipher.getInstance("RSA/ECB/PKCS1Padding");
    cipher.init(Cipher.DECRYPT_MODE, privateK);
    int inputLen = encryptedData.length;
    ByteArrayOutputStream out = new ByteArrayOutputStream();
    int offSet = 0;
    byte[] cache;
    int i = 0;
    // 對數據分段解密
    while (inputLen - offSet > 0) {
      if (inputLen - offSet > MAX_DECRYPT_BLOCK) {
        cache = cipher.doFinal(encryptedData, offSet, MAX_DECRYPT_BLOCK);
      } else {
        cache = cipher.doFinal(encryptedData, offSet, inputLen - offSet);
      }
      out.write(cache, 0, cache.length);
      i++;
      offSet = i * MAX_DECRYPT_BLOCK;
    }
    byte[] decryptedData = out.toByteArray();
    out.close();
    return decryptedData;
  }

  /**
   * <p>
   * 公鑰解密
   * </p>
   *
   * @param encryptedData 已加密數據
   * @param publicKey   公鑰(BASE64編碼)
   * @return
   * @throws Exception
   */
  public static byte[] decryptByPublicKey(byte[] encryptedData, String publicKey)
      throws Exception {
    byte[] keyBytes = Base64Utils.decode(publicKey);
    X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(keyBytes);
    KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
    Key publicK = keyFactory.generatePublic(x509KeySpec);
//    Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
    Cipher cipher = Cipher.getInstance("RSA/ECB/PKCS1Padding");
    cipher.init(Cipher.DECRYPT_MODE, publicK);
    int inputLen = encryptedData.length;
    ByteArrayOutputStream out = new ByteArrayOutputStream();
    int offSet = 0;
    byte[] cache;
    int i = 0;
    // 對數據分段解密
    while (inputLen - offSet > 0) {
      if (inputLen - offSet > MAX_DECRYPT_BLOCK) {
        cache = cipher.doFinal(encryptedData, offSet, MAX_DECRYPT_BLOCK);
      } else {
        cache = cipher.doFinal(encryptedData, offSet, inputLen - offSet);
      }
      out.write(cache, 0, cache.length);
      i++;
      offSet = i * MAX_DECRYPT_BLOCK;
    }
    byte[] decryptedData = out.toByteArray();
    out.close();
    return decryptedData;
  }

  /**
   * <p>
   * 公鑰加密
   * </p>
   *
   * @param sourcedata   源數據
   * @param publicKey 公鑰(BASE64編碼)
   * @return
   * @throws Exception
   */
  public static byte[] encryptByPublicKey(String sourcedata, String publicKey)
      throws Exception {
    byte[] data = sourcedata.getBytes();
    byte[] keyBytes = Base64Utils.decode(publicKey);
    X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(keyBytes);
    KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
    Key publicK = keyFactory.generatePublic(x509KeySpec);
    // 對數據加密
//    Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
    Cipher cipher = Cipher.getInstance("RSA/ECB/PKCS1Padding");
    cipher.init(Cipher.ENCRYPT_MODE, publicK);
    int inputLen = data.length;
    ByteArrayOutputStream out = new ByteArrayOutputStream();
    int offSet = 0;
    byte[] cache;
    int i = 0;
    // 對數據分段加密
    while (inputLen - offSet > 0) {
      if (inputLen - offSet > MAX_ENCRYPT_BLOCK) {
        cache = cipher.doFinal(data, offSet, MAX_ENCRYPT_BLOCK);
      } else {
        cache = cipher.doFinal(data, offSet, inputLen - offSet);
      }
      out.write(cache, 0, cache.length);
      i++;
      offSet = i * MAX_ENCRYPT_BLOCK;
    }
    byte[] encryptedData = out.toByteArray();
    out.close();
    return encryptedData;
  }

  /**
   * <p>
   * 私鑰加密
   * </p>
   *
   * @param data    源數據
   * @param privateKey 私鑰(BASE64編碼)
   * @return
   * @throws Exception
   */
  public static byte[] encryptByPrivateKey(byte[] data, String privateKey)
      throws Exception {
    byte[] keyBytes = Base64Utils.decode(privateKey);
    PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(keyBytes);
    KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
    Key privateK = keyFactory.generatePrivate(pkcs8KeySpec);
//    Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
    Cipher cipher = Cipher.getInstance("RSA/ECB/PKCS1Padding");
    cipher.init(Cipher.ENCRYPT_MODE, privateK);
    int inputLen = data.length;
    ByteArrayOutputStream out = new ByteArrayOutputStream();
    int offSet = 0;
    byte[] cache;
    int i = 0;
    // 對數據分段加密
    while (inputLen - offSet > 0) {
      if (inputLen - offSet > MAX_ENCRYPT_BLOCK) {
        cache = cipher.doFinal(data, offSet, MAX_ENCRYPT_BLOCK);
      } else {
        cache = cipher.doFinal(data, offSet, inputLen - offSet);
      }
      out.write(cache, 0, cache.length);
      i++;
      offSet = i * MAX_ENCRYPT_BLOCK;
    }
    byte[] encryptedData = out.toByteArray();
    out.close();
    return encryptedData;
  }

  /**
   * <p>
   * 獲取私鑰
   * </p>
   *
   * @param keyMap 密鑰對
   * @return
   * @throws Exception
   */
  public static String getPrivateKey(Map<String, Object> keyMap)
      throws Exception {
    Key key = (Key) keyMap.get(PRIVATE_KEY);
    return Base64Utils.encode(key.getEncoded());
  }

  /**
   * <p>
   * 獲取公鑰
   * </p>
   *
   * @param keyMap 密鑰對
   * @return
   * @throws Exception
   */
  public static String getPublicKey(Map<String, Object> keyMap)
      throws Exception {
    Key key = (Key) keyMap.get(PUBLIC_KEY);
    return Base64Utils.encode(key.getEncoded());
  }

  //  把byte[]元素之間添加空格，并轉化成字符串返回，
  public static String byteToString(byte[] resouce){
    StringBuffer sb = new StringBuffer();
    for (int i = 0; i < resouce.length; i++) {
      if (i == resouce.length-1) {
        sb.append(Byte.toString(resouce[i]));
      }else{
        sb.append(Byte.toString(resouce[i]));
        sb.append(" ");
      }
    }
    return sb.toString();

  }

  //  把字符串按照空格進行拆分成數組，然后轉化成byte[],返回
  public static byte[] stringToByte(String resouce){
    String[] strArr = resouce.split(" ");
    int len = strArr.length;
    byte[] clone = new byte[len];
    for (int i = 0; i < len; i++) {
      clone[i] = Byte.parseByte(strArr[i]);
    }

    return clone;

  }
}