Public and private keys must be used to install applications in iOS.

Apple officially generates a pair of public and private keys through asymmetric encryption.

First, there is a public key built into the iOS device, and the corresponding private key is saved in the Apple backend. When the developer uploads the app to the App Store, Apple uses the private key to sign the app. After iOS device users download the app, they use the public key to verify the signature, which ensures that the source of each app is official from Apple.

Second, the developer applies for a certificate from Apple's backend. The developer generates a pair of public and private keys on the local Mac, and transmits the public key to the developer's backend through the local sub-signature root certificate. Apple's backend uses Apple's private key. To sign the public key we uploaded, we will get something called a developer certificate, and a pp file containing app information. After compiling an app locally, sign the app with the local private key, and at the same time The pp file is packaged into the app, and then during installation, the iOS device obtains the certificate and uses Apple's public key to verify whether the signature of the certificate and the information in the pp file are correct. In this way, the proliferation of app installations is controlled.