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分类: Java

2010-11-11 11:42:47

教程由中文网整理校对发布(javaweb.cc)

  近些年DES使用越来越少,原因就在于其使用56位密钥,比较容易被破解,近些年来逐渐被AES替代,AES已经变成目前对称加密中最流 行算法之一;AES可以使用128、192、和256位密钥,并且用128位分组加密和解密数据。本文就简单介绍如何通过JAVA实现AES加密。

  1. JAVA实现

  闲话少许,掠过AES加密原理及算法,关于这些直接搜索专业网站吧,我们直接看JAVA的具体实现。

  1.1 加密

  代码有详细解释,不多废话。

  /**

  * 加密

  *

  * @param content 需要加密的内容

  * @param password 加密密码

  * @return

  */

  public static byte[] encrypt(String content, String password) {

  try {

  KeyGenerator kgen = KeyGenerator.getInstance("AES");

  kgen.init(128, new SecureRandom(password.getBytes()));

  SecretKey secretKey = kgen.generateKey();

  byte[] enCodeFormat = secretKey.getEncoded();

  SecretKeySpec key = new SecretKeySpec(enCodeFormat, "AES");

  Cipher cipher = Cipher.getInstance("AES");// 创建密码器

  byte[] byteContent = content.getBytes("utf-8");

  cipher.init(Cipher.ENCRYPT_MODE, key);// 初始化

  byte[] result = cipher.doFinal(byteContent);

  return result; // 加密

  } catch (NoSuchAlgorithmException e) {

  e.printStackTrace();

  } catch (NoSuchPaddingException e) {

  e.printStackTrace();

  } catch (InvalidKeyException e) {

  e.printStackTrace();

  } catch (UnsupportedEncodingException e) {

  e.printStackTrace();

  } catch (IllegalBlockSizeException e) {

  e.printStackTrace();

  } catch (BadPaddingException e) {

  e.printStackTrace();

  }

  return null;

  }

  /**

  * 加密

  *

  * @param content 需要加密的内容

  * @param password 加密密码

  * @return

  */

  public static byte[] encrypt(String content, String password) {

  try {

  KeyGenerator kgen = KeyGenerator.getInstance("AES");

  kgen.init(128, new SecureRandom(password.getBytes()));

  SecretKey secretKey = kgen.generateKey();

  byte[] enCodeFormat = secretKey.getEncoded();

  SecretKeySpec key = new SecretKeySpec(enCodeFormat, "AES");

  Cipher cipher = Cipher.getInstance("AES");// 创建密码器

  byte[] byteContent = content.getBytes("utf-8");

  cipher.init(Cipher.ENCRYPT_MODE, key);// 初始化

  byte[] result = cipher.doFinal(byteContent);

  return result; // 加密

  } catch (NoSuchAlgorithmException e) {

  e.printStackTrace();

  } catch (NoSuchPaddingException e) {

  e.printStackTrace();

  } catch (InvalidKeyException e) {

  e.printStackTrace();

  } catch (UnsupportedEncodingException e) {

  e.printStackTrace();

  } catch (IllegalBlockSizeException e) {

  e.printStackTrace();

  } catch (BadPaddingException e) {

  e.printStackTrace();

  }

  return null;

  }

  2.2 解密

  代码有详细注释,不多废话

  注意:解密的时候要传入byte数组

  view plaincopy to clipboardprint?

  /**解密

  * @param content 待解密内容

  * @param password 解密密钥

  * @return

  */

  public static byte[] decrypt(byte[] content, String password) {

  try {

  KeyGenerator kgen = KeyGenerator.getInstance("AES");

  kgen.init(128, new SecureRandom(password.getBytes()));

  SecretKey secretKey = kgen.generateKey();

  byte[] enCodeFormat = secretKey.getEncoded();

  SecretKeySpec key = new SecretKeySpec(enCodeFormat, "AES");

  Cipher cipher = Cipher.getInstance("AES");// 创建密码器

  cipher.init(Cipher.DECRYPT_MODE, key);// 初始化

  byte[] result = cipher.doFinal(content);

  return result; // 加密

  } catch (NoSuchAlgorithmException e) {

  e.printStackTrace();

  } catch (NoSuchPaddingException e) {

  e.printStackTrace();

  } catch (InvalidKeyException e) {

  e.printStackTrace();

  } catch (IllegalBlockSizeException e) {

  e.printStackTrace();

  } catch (BadPaddingException e) {

  e.printStackTrace();

  }

  return null;

  }

  /**解密

  * @param content 待解密内容

  * @param password 解密密钥

  * @return

  */

  public static byte[] decrypt(byte[] content, String password) {

  try {

  KeyGenerator kgen = KeyGenerator.getInstance("AES");

  kgen.init(128, new SecureRandom(password.getBytes()));

  SecretKey secretKey = kgen.generateKey();

  byte[] enCodeFormat = secretKey.getEncoded();

  SecretKeySpec key = new SecretKeySpec(enCodeFormat, "AES");

  Cipher cipher = Cipher.getInstance("AES");// 创建密码器

  cipher.init(Cipher.DECRYPT_MODE, key);// 初始化

  byte[] result = cipher.doFinal(content);

  return result; // 加密

  } catch (NoSuchAlgorithmException e) {

  e.printStackTrace();

  } catch (NoSuchPaddingException e) {

  e.printStackTrace();

  } catch (InvalidKeyException e) {

  e.printStackTrace();

  } catch (IllegalBlockSizeException e) {

  e.printStackTrace();

  } catch (BadPaddingException e) {

  e.printStackTrace();

  }

  return null;

  }


2.3 测试代码

  String content = "test";

  String password = "12345678";

  //加密

  System.out.println("加密前:" + content);

  byte[] encryptResult = encrypt(content, password);

  //解密

  byte[] decryptResult = decrypt(encryptResult,password);

  System.out.println("解密后:" + new String(decryptResult));

  String content = "test";

  String password = "12345678";

  //加密

  System.out.println("加密前:" + content);

  byte[] encryptResult = encrypt(content, password);

  //解密

  byte[] decryptResult = decrypt(encryptResult,password);

  System.out.println("解密后:" + new String(decryptResult));

  输出结果如下:

  加密前:test

  解密后:test

  2.4 容易出错的地方

  但是如果我们将测试代码修改一下,如下:

  String content = "test";

  String password = "12345678";

  //加密

  System.out.println("加密前:" + content);

  byte[] encryptResult = encrypt(content, password);

  try {

  String encryptResultStr = new String(encryptResult,"utf-8");

  //解密

  byte[] decryptResult = decrypt(encryptResultStr.getBytes("utf-8"),password);

  System.out.println("解密后:" + new String(decryptResult));

  } catch (UnsupportedEncodingException e) {

  e.printStackTrace();

  }

  String content = "test";

  String password = "12345678";

  //加密

  System.out.println("加密前:" + content);

  byte[] encryptResult = encrypt(content, password);

  try {

  String encryptResultStr = new String(encryptResult,"utf-8");

  //解密

  byte[] decryptResult = decrypt(encryptResultStr.getBytes("utf-8"),password);

  System.out.println("解密后:" + new String(decryptResult));

  } catch (UnsupportedEncodingException e) {

  e.printStackTrace();

  }

  则,系统会报出如下异常:

  javax.crypto.IllegalBlockSizeException: Input length must be multiple of 16 when decrypting with padded cipher

  at com.sun.crypto.provider.SunJCE_f.b(DashoA13*..)

  at com.sun.crypto.provider.SunJCE_f.b(DashoA13*..)

  at com.sun.crypto.provider.AESCipher.engineDoFinal(DashoA13*..)

  at javax.crypto.Cipher.doFinal(DashoA13*..)

  这主要是因为加密后的byte数组是不能强制转换成字符串的,换言之:字符串和byte数组在这种情况下不是互逆的;要避免这种情况,我们需要做一些修订,可以考虑将二进制数据转换成十六进制表示,主要有如下两个方法:

  2.4.1将二进制转换成16进制

  /**将二进制转换成16进制

  * @param buf

  * @return

  */

  public static String parseByte2HexStr(byte buf[]) {

  StringBuffer sb = new StringBuffer();

  for (int i = 0; i < buf.length; i++) {

  String hex = Integer.toHexString(buf[i] & 0xFF);

  if (hex.length() == 1) {

  hex = '0' + hex;

  }

  sb.append(hex.toUpperCase());

  }

  return sb.toString();

  }

  /**将二进制转换成16进制

  * @param buf

  * @return

  */

  public static String parseByte2HexStr(byte buf[]) {

  StringBuffer sb = new StringBuffer();

  for (int i = 0; i < buf.length; i++) {

  String hex = Integer.toHexString(buf[i] & 0xFF);

  if (hex.length() == 1) {

  hex = '0' + hex;

  }

  sb.append(hex.toUpperCase());

  }

  return sb.toString();

  }

  2.4.2 将16进制转换为二进制

  /**将16进制转换为二进制

  * @param hexStr

  * @return

  */

  public static byte[] parseHexStr2Byte(String hexStr) {

  if (hexStr.length() < 1)

  return null;

  byte[] result = new byte[hexStr.length()/2];

  for (int i = 0;i< hexStr.length()/2; i++) {

  int high = Integer.parseInt(hexStr.substring(i*2, i*2+1), 16);

  int low = Integer.parseInt(hexStr.substring(i*2+1, i*2+2), 16);

  result[i] = (byte) (high * 16 + low);

  }

  return result;

  }


/**将16进制转换为二进制

  * @param hexStr

  * @return

  */

  public static byte[] parseHexStr2Byte(String hexStr) {

  if (hexStr.length() < 1)

  return null;

  byte[] result = new byte[hexStr.length()/2];

  for (int i = 0;i< hexStr.length()/2; i++) {

  int high = Integer.parseInt(hexStr.substring(i*2, i*2+1), 16);

  int low = Integer.parseInt(hexStr.substring(i*2+1, i*2+2), 16);

  result[i] = (byte) (high * 16 + low);

  }

  return result;

  }

  然后,我们再修订以上测试代码,如下:

  String content = "test";

  String password = "12345678";

  //加密

  System.out.println("加密前:" + content);

  byte[] encryptResult = encrypt(content, password);

  String encryptResultStr = parseByte2HexStr(encryptResult);

  System.out.println("加密后:" + encryptResultStr);

  //解密

  byte[] decryptFrom = parseHexStr2Byte(encryptResultStr);

  byte[] decryptResult = decrypt(decryptFrom,password);

  System.out.println("解密后:" + new String(decryptResult));

  String content = "test";

  String password = "12345678";

  //加密

  System.out.println("加密前:" + content);

  byte[] encryptResult = encrypt(content, password);

  String encryptResultStr = parseByte2HexStr(encryptResult);

  System.out.println("加密后:" + encryptResultStr);

  //解密

  byte[] decryptFrom = parseHexStr2Byte(encryptResultStr);

  byte[] decryptResult = decrypt(decryptFrom,password);

  System.out.println("解密后:" + new String(decryptResult));

  测试结果如下:

  加密前:test

  加密后:73C58BAFE578C59366D8C995CD0B9D6D

  解密后:test

  2.5 另外一种加密方式

  还有一种加密方式,大家可以参考如下:

  /**

  * 加密

  *

  * @param content 需要加密的内容

  * @param password 加密密码

  * @return

  */

  public static byte[] encrypt2(String content, String password) {

  try {

  SecretKeySpec key = new SecretKeySpec(password.getBytes(), "AES");

  Cipher cipher = Cipher.getInstance("AES/ECB/NoPadding");

  byte[] byteContent = content.getBytes("utf-8");

  cipher.init(Cipher.ENCRYPT_MODE, key);// 初始化

  byte[] result = cipher.doFinal(byteContent);

  return result; // 加密

  } catch (NoSuchAlgorithmException e) {

  e.printStackTrace();

  } catch (NoSuchPaddingException e) {

  e.printStackTrace();

  } catch (InvalidKeyException e) {

  e.printStackTrace();

  } catch (UnsupportedEncodingException e) {

  e.printStackTrace();

  } catch (IllegalBlockSizeException e) {

  e.printStackTrace();

  } catch (BadPaddingException e) {

  e.printStackTrace();

  }

  return null;

  }

  /**

  * 加密

  *

  * @param content 需要加密的内容

  * @param password 加密密码

  * @return

  */

  public static byte[] encrypt2(String content, String password) {

  try {

  SecretKeySpec key = new SecretKeySpec(password.getBytes(), "AES");

  Cipher cipher = Cipher.getInstance("AES/ECB/NoPadding");

  byte[] byteContent = content.getBytes("utf-8");

  cipher.init(Cipher.ENCRYPT_MODE, key);// 初始化

  byte[] result = cipher.doFinal(byteContent);

  return result; // 加密

  } catch (NoSuchAlgorithmException e) {

  e.printStackTrace();

  } catch (NoSuchPaddingException e) {

  e.printStackTrace();

  } catch (InvalidKeyException e) {

  e.printStackTrace();

  } catch (UnsupportedEncodingException e) {

  e.printStackTrace();

  } catch (IllegalBlockSizeException e) {

  e.printStackTrace();

  } catch (BadPaddingException e) {

  e.printStackTrace();

  }

  return null;

  }

  这种加密方式有两种限制

  密钥必须是16位的

  待加密内容的长度必须是16的倍数,如果不是16的倍数,就会出如下异常:

  javax.crypto.IllegalBlockSizeException: Input length not multiple of 16 bytes

  at com.sun.crypto.provider.SunJCE_f.a(DashoA13*..)

  at com.sun.crypto.provider.SunJCE_f.b(DashoA13*..)

  at com.sun.crypto.provider.SunJCE_f.b(DashoA13*..)

  at com.sun.crypto.provider.AESCipher.engineDoFinal(DashoA13*..)

  at javax.crypto.Cipher.doFinal(DashoA13*..)

  要解决如上异常,可以通过补全传入加密内容等方式进行避免。


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