JAVA实现AES加密

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1. 因子
       上次介绍了《JAVA实现AES加密》，中间提到近些年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。
2. 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。
2.1 加密
代码有详细解释，不多废话。
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/**
* 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
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/**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
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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：
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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
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/**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
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/**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：
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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：
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/**
      * 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。