android AES对称加密算法使用实例

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代码是最好的注释！

public class AES {

   public static String mSeed = "leichxxxxx;

/*   public static String encrypt(String seed, String cleartext)
           throws Exception {
       byte[] rawKey = getRawKey(seed.getBytes());
       byte[] result = encrypt(rawKey, cleartext.getBytes());
       return toHex(result);
   }

   public static String decrypt(String seed, String encrypted)
           throws Exception {
       byte[] rawKey = getRawKey(seed.getBytes());
       byte[] enc = toByte(encrypted);
       byte[] result = decrypt(rawKey, enc);
       return new String(result);
   }*/

   public static byte[] encryptExt(String seed, byte[] cleartext)
           throws Exception {
       byte[] rawKey = getRawKey(seed.getBytes());
       byte[] result = encrypt(rawKey, cleartext);
       return result;
   }

   public static byte[] decryptExt(String seed, byte[] encrypted)
           throws Exception {
       byte[] rawKey = getRawKey(seed.getBytes());
       byte[] enc = encrypted;
       byte[] result = decrypt(rawKey, enc);
       return result;
   }

   private static byte[] getRawKey(byte[] seed) throws Exception {
       KeyGenerator kgen = KeyGenerator.getInstance("AES");
       SecureRandom sr = SecureRandom.getInstance("SHA1PRNG", "Crypto");
       sr.setSeed(seed);
       kgen.init(128, sr); // 192 and 256 bits may not be available
       SecretKey skey = kgen.generateKey();
       byte[] raw = skey.getEncoded();
       return raw;
   }

   private static byte[] encrypt(byte[] raw, byte[] clear) throws Exception {
       SecretKeySpec skeySpec = new SecretKeySpec(raw, "AES");
       Cipher cipher = Cipher.getInstance("AES");
       cipher.init(Cipher.ENCRYPT_MODE, skeySpec, new IvParameterSpec(
               new byte[cipher.getBlockSize()]));
       byte[] encrypted = cipher.doFinal(clear);
       return encrypted;
   }

   private static byte[] decrypt(byte[] raw, byte[] encrypted)
           throws Exception {
       SecretKeySpec skeySpec = new SecretKeySpec(raw, "AES");
       Cipher cipher = Cipher.getInstance("AES");
       cipher.init(Cipher.DECRYPT_MODE, skeySpec, new IvParameterSpec(
               new byte[cipher.getBlockSize()]));
       byte[] decrypted = cipher.doFinal(encrypted);
       return decrypted;
   }

   private static byte[] toByte(String hexString) {
       int len = hexString.length() / 2;
       byte[] result = new byte[len];
       for (int i = 0; i < len; i++)
           result[i] = Integer.valueOf(hexString.substring(2 * i, 2 * i + 2),
                   16).byteValue();
       return result;
   }

   private static String toHex(byte[] buf) {
       if (buf == null)
           return "";
       StringBuffer result = new StringBuffer(2 * buf.length);
       for (int i = 0; i < buf.length; i++) {
           appendHex(result, buf[i]);
       }
       return result.toString();
   }

   private final static String HEX = "0123456789ABCDEF";

   private static void appendHex(StringBuffer sb, byte b) {
       sb.append(HEX.charAt((b >> 4) & 0x0f)).append(HEX.charAt(b & 0x0f));
   }

   public static void Test() {
       String source = "1234567890abcdefghijklmnopqrstuvwxyz1234567890abcdefghijklmnopqrstuvwxyz";
       try {
           Log.d(CONST.TAG, "source:" + source);
           byte[] output = encryptExt(mSeed, source.getBytes());
           Log.d(CONST.TAG, "output:" + output);
           byte[] output2 = decryptExt(mSeed, output);
           Log.d(CONST.TAG, "output2:" + output2);
       } catch (Exception e) {
           e.printStackTrace();
       }
   }

}

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