I guess you didn't really read the article so I'll put it here : > They intercepted one billion messages, but they couldn't read them at first because they were encrypted. It wasn’t until late 2020 that they managed to decrypt them.

The article is extremely vague on how they did this. The one big red flag though is that the protocol for the messenger in the article was a bespoke secret design by a single person who wasn't a cryptographer and not a well vetted public one.

I would love to see a technical analysis of the supposed end-to-end encryption methodology used here.