传输加密

https://segmentfault.com/a/1190000018083089

base64
https://www.cnblogs.com/LiuPan2016/p/9935498.html

 /*
  * Base64加密
  */
  static String encodeBase64(String data){
    var content = utf8.encode(data);
    var digest = base64Encode(content);
    return digest;
  }
  /*
  * Base64解密
  */
  static String decodeBase64(String data){
    return String.fromCharCodes(base64Decode(data));
  }

crypto 2.1.1+1
https://pub.flutter-io.cn/packages/crypto