Caching user data

[lgrahl]

Yep, this is going to be a very controversial idea but bear with me. We could cache user data, so it doesn't need to be requested from the Threema app every time. This could be beneficial for preview images, images in general, voice messages, videos and potentially even for the conversation history.

Now, you may say this is a preposterous idea and what on earth am I thinking because my original design tried very hard to prevent exactly that: Having the user data in several places. But what if this data is encrypted twice, first by the session password and then by a secret key that needs to be requested from the app? And this should of course be an optional feature.

[dbrgn]

Synchronization would be quite challenging, since the app would first need to know what information is available.

[lgrahl]

UUIDs could be used for that. IIRC they have already been used for several items in the database.