19 points ·
I can think of easier ways of compromising the data besides brute forcing the keys, off the top of my head, and I'm just some schmuck. Relevant XKCD: https://xkcd.com/538/
1. Compromise their endpoint with a malicious app on the app store.
2. Gain physical access to the device and compromise it. Use your imagination – pickpocket, traffic stop or customs inspection by a compromised agent, seduce them with a honeypot, etc.
3. Socially engineer them to mistakingly add you to their group chats.
4. SIM swap
Signal might be fine for journalists, criminals, cheating spouses, and general privacy _when used properly with good OpSec_ but nation state adversaries have significantly greater resources than your average attacker, and thus require more significant security.