So if I already have an Android app in the hands of many customers, and I sign the app myself with an APK, but want to start using Play App Signing and let Google generate the app signing key, won't my current customers be unable to update the app thereafter? My understanding is that updates will only be accepted on the mobile device if the app signing cert is the same for the update as for the already-installed app. If I start using Play App Signing and let Google generate the (new) app signing key, obviously the cert will change. Have I got this right? How best to handle this situation?
If I start letting Google generate my app signing key, how do existing customers get app updates?
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2 Answers
So what happens is you sign the app with key A. Google can recognize its you from that key. Google will generate key B, save it, and resign your app with B. Then it will put that version available for download.
When you later update the app, it will see key A, verify the app, and resign it with key B, the same key it generated last time. So it will have the same signature and will be accepted by the mobile devices as an update.
So updates work. You are allowing Google to purposely man in the middle you and you have the risk that Google will decide to alter your app before release. But most people find that an acceptable risk (they have no real reason to do it and a lot of reasons not to).
You can provide Google with the key you wish them to sign the APKs with. You don't have to let Google generate a new key. Make sure to open the advanced options when enrolling and not use the default option for this feature, then follow the instructions.
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