

MLS only deals with encryption and key management, which is great but that’s been a “solved” problem since TextSecure (now Signal) introduced the TextSecure Protocol (now the Signal Protocol) in 2013.
What I’m aware is missing with RCS / MLS compared to Signal (someone with more recent knowledge please correct me):
- Sealed sender so only the recipient knows who sent the message.
- Not storing metadata or logs.
- No built in crash reports.
- Private contact discovery.
- Published government requests providing evidence that they don’t have any data.
- Open source client.
- Looking at the Google Play store, Google’s Messenger shares precise location data with third parties, Signal doesn’t.
- Also on the Google Play store, Google’s Messenger app list a lot of data collected. Signal only lists phone number.
to add even more to what’s already been said, even if Signal’s infrastructure was compromised and they could see messages traveling through their servers, each one is encrypted, the keys are rotated with every message (cracking one, which is nearly impossible, doesn’t give you access to previous or future messages), and thanks to Sealed Sender, only the recipient knows who a message came from. There are many other layers that they’ve engineered to ensure they can’t know anything about you, like private contact discovery, using secure enclaves, remote attestation, etc.