Android客户端与java服务端AES加解密

AES加密分两大块来说吧（仅在客户端加解密和客户端加密服务端解密）,

（一）针对于android客户端加解密来说，比如登陆时候将用户名和密码存储到sharedpreferences 中对于解密位数没有要求，8位、16位、32位都可以成功加解密代码如下（可以直接作为一个utils封装成一个jar来调用）：（二）

public class AESUtil {

   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);
     }
   
     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); 
         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;
     }
   
     @SuppressWarnings("unused")
  private static String toHex(String txt) {
         return toHex(txt.getBytes());
     }
   
     @SuppressWarnings("unused")
  private static String fromHex(String hex) {
         return new String(toByte(hex));
     }
   
     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));
     }
}  

代码解析如下：
主要看加密encryp（）和解密decrypt（）方法；参数一可以选用手机唯一的id作为key因为每个手机都有唯一的识别key通过此加密不容易被破解。参数二则为需要加密的内容。获取手机识别key的id方法如下：

public class GetTelphoneInfo {

    public static String getImsi(Context context) {
    TelephonyManager tm = (TelephonyManager) context.getSystemService(Context.TELEPHONY_SERVICE);
    String _imsi = tm.getSubscriberId();
    if(_imsi != null && !_imsi.equals("")){
    return _imsi;
     }
  return "未知";
   }
}

（二） android客户端加密，java服务端解密

和以上android客户端加解密唯一不同的是：加解密的内容需要16位的字符。因为这个问题，把8位，16位，32位的加解密都试了一遍，结果只有16位的可以（android客户端加密，java服务端解密内容一致）加密机制为16的倍数。客户端加密代码如下：

/**
 *
 * @param source 被加密的字符串
 * @param key  加密key
 * @return 加密过后的字符串
 */
public static String encrypt4AES(String source, String key) {
    try {
        byte[] iv = key.substring(0,16).getBytes("utf-8");
        IvParameterSpec zeroIv = new IvParameterSpec(iv);
        SecretKeySpec key1 = new SecretKeySpec(iv, "AES");
        Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
        cipher.init(Cipher.ENCRYPT_MODE, key1, zeroIv);
        byte[] encryptedData = cipher.doFinal(source.getBytes("utf-8"));
        String encryptResultStr = parseByte2HexStr(encryptedData);
        return encryptResultStr; // 加密
    } catch (Exception e) {
        e.printStackTrace();
        return "";
    }
}