security

Code Signing and Sideloaded Apps: What a Signature Proves

A signature tells you who published an app and that it has not been altered since. It does not tell you the app is good. Knowing the difference matters most when installing outside an app store.

What code signing is

Code signing is the process of digitally signing executables and scripts to confirm the author and guarantee the code has not been changed since it was signed. Operating systems check signatures before running or installing software.

What it proves, and what it does not

It proves the software came from the holder of a particular signing key.
It proves the file has not been modified since signing.
It does not prove the publisher is trustworthy or the software is safe.

Installing outside a store

On Android, apps can be installed from an APK file once the user allows installs from that source. That flexibility is useful for testing builds, and it removes a layer of store review. For your own test builds, sign them consistently, distribute them from a source you control and remove the permission when you are done.

How a good install guide should read

From a developer's point of view, the best user-facing install guides put verification first: how to tell the genuine app from a clone, then the steps for each platform, then which security setting is being changed and why. An example that follows that order, in Traditional Chinese, is an iOS and Android installation guide that opens by explaining how to distinguish the official app from copycat apps and then covers APK security settings (夜色娛樂城APP安裝教學). Whatever you ship, documenting the verification step is part of the security model.

For your own projects, protect the signing key as carefully as a production password. Anyone who has it can publish updates as you.

last updated 2026-10-20