RSA实例 java 安全

public class RSAUtil {   public static String RSADecode(String password) {      String pwd = password;      try {         password = org.apache.commons.lang.StringUtils.substring(pwd, 0,               256);         byte[] en_result = RSAUtil.hexStringToBytes(password);         byte[] de_result = RSAUtil.decrypt(RSAUtil.getKeyPair()               .getPrivate(), en_result);         StringBuffer sb = new StringBuffer();         sb.append(new String(de_result));         password = sb.reverse().toString();         password = URLDecoder.decode(password, "UTF-8");         return password;      } catch (Exception e) {         e.printStackTrace();         return "";      }   }   public static KeyPair getKeyPair() throws Exception {      File file = new File("c:/RSAKey.txt");      InputStream fis = new FileInputStream(file);      ObjectInputStream oos = new ObjectInputStream(fis);      KeyPair kp = (KeyPair) oos.readObject();      oos.close();      if(fis!=null){         fis.close();      }      return kp;   }   public static byte[] encrypt(PublicKey pk, byte[] data) throws Exception {      try {         Cipher cipher = Cipher.getInstance("RSA",               new org.bouncycastle.jce.provider.BouncyCastleProvider());         cipher.init(Cipher.ENCRYPT_MODE, pk);         int blockSize = cipher.getBlockSize();         int outputSize = cipher.getOutputSize(data.length);         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);            i++;         }         return raw;      } catch (Exception e) {         throw new Exception(e.getMessage());      }   }   public static byte[] decrypt(PrivateKey pk, byte[] raw) throws Exception {      try {         Cipher cipher = Cipher.getInstance("RSA",               new org.bouncycastle.jce.provider.BouncyCastleProvider());         cipher.init(Cipher.DECRYPT_MODE, pk);         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 Exception(e.getMessage());      }   }   public static byte[] hexStringToBytes(String hexString) {      if (hexString == null || hexString.equals("")) {         return null;      }      hexString = hexString.toUpperCase();      int length = hexString.length() / 2;      char[] hexChars = hexString.toCharArray();      byte[] d = new byte[length];      for (int i = 0; i < length; i++) {         int pos = i * 2;         d[i] = (byte) (charToByte(hexChars[pos]) << 4 | charToByte(hexChars[pos + 1]));      }      return d;   }   private static byte charToByte(char c) {      return (byte) "0123456789ABCDEF".indexOf(c);   }   private static String  getServletPath(){      return getRequest().getServletContext().getRealPath("");   }   private static HttpServletRequest getRequest(){      RequestAttributes requestAttributes = RequestContextHolder.getRequestAttributes();      if (requestAttributes instanceof ServletRequestAttributes) {         return ((ServletRequestAttributes) requestAttributes).getRequest();      }      return null;   }   public static void genKey() throws Exception {      KeyPairGenerator keyPairGen = KeyPairGenerator.getInstance("RSA",            new org.bouncycastle.jce.provider.BouncyCastleProvider());      final int KEY_SIZE = 1024;      keyPairGen.initialize(KEY_SIZE, new SecureRandom());      KeyPair KP = keyPairGen.generateKeyPair();      PublicKey publicKey = KP.getPublic();      PrivateKey prKey = KP.getPrivate();      System.out.println(publicKey);      FileOutputStream ko = new FileOutputStream("c:/RSAKey.txt");      ObjectOutputStream fo = new ObjectOutputStream(ko);      fo.writeObject(KP);      FileOutputStream out = new FileOutputStream("c:/PublicKey.txt");      ObjectOutputStream fileOut = new ObjectOutputStream(out);      fileOut.writeObject(publicKey);      FileOutputStream outPrivate = new FileOutputStream("c:/PrivateKey.txt");      ObjectOutputStream privateOut = new ObjectOutputStream(outPrivate);      privateOut.writeObject(prKey);      ko.close();      out.close();      outPrivate.close();   }  public static void main(String[] args) throws Exception {      //genKey();      RSAPublicKey rsap = (RSAPublicKey) RSAUtil.getKeyPair().getPublic();      System.out.println(rsap.getModulus());      String test = "hello world";      PublicKey pk = getKeyPair().getPublic();      System.out.println(pk.getEncoded().toString());      PrivateKey ck = getKeyPair().getPrivate();      byte[] en_test = encrypt(pk, test.getBytes());      byte[] de_test = decrypt(ck, en_test);      System.out.println(new String(de_test));   }}