Hector Martin

There is no magical pixie dust encryption algorithm that will protect your messages in such a way that whatever new version of Signal can access them but no other app or user can (on a desktop). If you have local access it's game over.

How about a non-magical average good encryption scheme where messages stores are encrypted using a password as salt? I don't know why you need to be condescending or exasperated about something as basic as encryption at rest.

What's the point? So you save the messages encrypted, import them, and then what? They're going to be decrypted to be useful, with credentials that any other app can hijack out of the running Signal instance even if they're encrypted "at rest".

If you encrypt at rest with a password based key (using KDF) that you don't store anywhere, and decrypt only chunks of the data at rest to store in memory, then you are limiting the attack surface. Also, this helps against device theft where they don't conrol your running app

Unless you want to input your password for every single message you view, the key has to be in memory while you use the app, at which point any other process can grab it.

You're solving these problems with the wrong, insufficient solution. This isn't Signal's job. Use sandboxing or user isolation to protect apps from each other. Use FDE and lock screens to protect against device theft.

It may not be Signal's job, but if it wants to not be an app just for security experts, you should not expect users to know that. It should protect at least against the attacks it can. Not everytime access to disk = full control

So you expect users to know which apps implement their own protections, and all developers to do so safely and effectively? Instead of just turning on FDE? If you're a user concerned with device theft, you should know about FDE. And if you don't we have a user education problem.