1. 因子
上次介绍了
《JAVA实现DES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。
- /**
- * 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
- /**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));
输出结果如下:
加密前:test
解密后: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();
- }
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*..)
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();
- }
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;
- }
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));
测试结果如下:
加密前:test
加密后:73C58BAFE578C59366D8C995CD0B9D6D
解密后: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;
- }
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*..)
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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