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Wonderfall 2022-01-07 20:32:51 +01:00
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content/posts/fdroid-issues.md
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@ -18,7 +18,7 @@ To understand why this is a problem, you'll have to understand a bit about F-Dro
Unlike other repositories, F-Droid signs all the apps in the main repository with **its own signing keys** at the exception of the very few [reproducible builds](https://f-droid.org/en/docs/Reproducible_Builds/). A signature is a mathematical scheme that guarantees the authenticity of the applications you download. Upon the installation of an app, Android pins the signature across the entire OS (including user profiles): that's what we call a *trust-on-first-use* model since all subsequent updates of the app must have the corresponding signature to be installed.
Normally, the developer is supposed to sign their own app prior to its upload on a distribution channel, whether that is a website or a traditional repository (or both). You don't have to trust the source (usually recommended by the developer) except for the first installation: future updates will have their authenticity cryptographically guaranteed. The issue with F-Droid is that all apps are signed by the same party (F-Droid) which is also not the developer. You're now adding another party you'll have to trust since you still have to trust the developer, which isn't ideal: **the fewer parties, the better**.
Normally, the developer is supposed to sign their own app prior to its upload on a distribution channel, whether that is a website or a traditional repository (or both). You don't have to trust the source (usually recommended by the developer) except for the first installation: future updates will have their authenticity cryptographically guaranteed. The issue with F-Droid is that all apps are signed by the same party (F-Droid) which is also not the developer. You're now adding another party you'll have to trust since **you still have to trust the developer** anyway, which isn't ideal: **the fewer parties, the better**.
On the other hand, Play Store now manages the app signing keys too, as [Play App Signing](https://developer.android.com/studio/publish/app-signing#app-signing-google-play) is required for app bundles which are required for new apps since August 2021. These signing keys can be uploaded or automatically generated, and are securely stored by [Google Cloud Key Management Service](https://services.google.com/fh/files/misc/security_whitepapers_march2018.pdf). It should be noted that the developer still has to sign the app with **an upload key** so that Google can verify its authenticity before signing it with the app signing key. For apps created before August 2021 that may have [not opted in Play App Signing](https://developer.android.com/studio/publish/app-signing#opt-out) yet, the developer still manages the private key and is responsible for its security, as a compromised private key can allow a third party to sign and distribute malicious code. Additionally, Google is pushing [code transparency for app bundles](https://developer.android.com/guide/app-bundle/code-transparency).