But to be fair nobody does anything from scratch. Most people were in school at least for a few years. If you code, you’ve probably read a lot of code and documentation, if you draw you probably saw a lot of drawings, if you play chess you probably studied a lot of different games.

Signal could still (at least for a short period of time) read everything. Whisper System just has to push a Signal Update that no longer encrypts. It would probably be noticed pretty soon. And no not because of the source code. The source code is what they claim to ise to build the applications but they could easily apply patches before they build. You’d have to reverse engineer the compiled applications ro see if there is code that’s probably not in the source.

This kind of problem is typically way smaller in projects that actively encourage building the clients from source yourself - which Whister System/Signal does not.

Facebook added the encryption in the first place because so many people were leaving for Signal and Threema (and Telegram but that’s another security nightmare).

Why not save a step, fuck bitlocker, and use veracrypt to encrypt your drive in the first place?