Friends who have installed the APP through AISI Assistant know that you don't need to enter Apple's ID and password to install the APP, so some people say that the principle of AISI Assistant installing the app is the sharing of Apple ID accounts.

First, download iPA installation files to your own platform through Apple's official APP Store, and then simulate iTunes to distribute applications through Apple's items-services protocol.

Aisi assistant not only shared the Apple ID, but also re-signed the iPA package. Aisi Assistant exploited a loophole, because developers need real machine debugging when developing apps for Apple devices, so Apple allows iPA packages signed by developers' certificates to be directly installed on Apple devices.

Aisi assistant buys the APP through his registered Apple ID and downloads it to his own server, and then re-signs iPA with his own corporate or personal certificate, so that many apps can be installed directly, and even some paid apps can be installed. This is why there is flashback, because the certificate has expired, so the concept of flashback repair has emerged, that is, changing a batch of certificates to re-sign the APP.