This can be solved by a nobus backdoor.

> if you install Signal on your Android, the apk was signed by Signal, sent to Google and distributed by Google. Google cannot modify it, because Signal has to sign

I'd stress that for specifically Signal this seems to indeed still be true, but almost apps on Google Play are now signed by Google (with keys either generated by them or provided to them), and even customized by Google for your specific system.

Google requires it for all apps created after August 2021. *

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> On Android there are verifier apps that allow you to check that.

If you mean Accrescent, it only checks the app's signature, not the hash of the individual versions.

I only know APK redistributors such as apkmirror that might let you check the individual app version, but they don't have API access and only host some apps.

And again, now almost apps on Google Play are signed by Google and customized on the fly for your device, so you typically can't really confront them.

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* Except that apparently, since a couple months ago Google allows you to use their HSMs?

Even this magnanimous concession though is “strictly for enterprise organizations with mandatory compliance, regulatory, or policy requirements to retain key custody in an external Google Cloud KMS instance” (https://developers.google.com/android-publisher/api-ref/rest...).

There's some chance that they can't access these keys; but the app needs to be compiled on their servers, so yeah, plenty of ways for them to meddle with it, and probably even to issue signing requests.

This seems to have been introduced in July, it's the first time I hear of it