No, you can look at the downloaded software installer. Generally, SIXX ends with signed software, and sis ends with unsigned software, so you need to sign it yourself.

In fact, many free softwares have been signed up, such as "Pocket Baidu" and "Mobile QQ".

If you encounter software that needs to be signed, you need to get the certificate of the mobile phone first, and then sign the unsigned software with the certificate of the mobile phone, so that you can install it normally.