1. 因子
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。
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" ); byte [] byteContent = content.getBytes( "utf-8" ); cipher.init(Cipher.ENCRYPT_MODE, key); byte [] result = cipher.doFinal(byteContent); return result; } 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
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" ); cipher.init(Cipher.DECRYPT_MODE, key); byte [] result = cipher.doFinal(content); return result; } 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" ; System.out.println("加密前:" + content); byte [] encryptResult = encrypt(content, password); 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" ; System.out.println("加密前:" + content); byte [] encryptResult = encrypt(content, password); try { String encryptResultStr = new String(encryptResult, "utf-8" ); 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
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
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" ; System.out.println("加密前:" + content); byte [] encryptResult = encrypt(content, password); String encryptResultStr = parseByte2HexStr(encryptResult); System.out.println("加密后:" + encryptResultStr); 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:
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); byte [] result = cipher.doFinal(byteContent); return result; } 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。