Rooms can be encrypted - in fact its enabled by default now for all new rooms, but rooms that are public don't make sense to encrypt as anyone is able to find/join, and what would be the point of encryption if anyone can just join and access the data anyway?
I will say that Matrix is not as easy, intuitive or as feature-polished as Signal and I think we can thank Signal's decision to not attempt federation for how much better it is at some things than Matrix. That said, Matrix is a great alternative, but I'm not asking my friends/family to join just yet.
Figured I'd repost because I see Session being recommended again.
======== Original Post: https://lemmy.ml/comment/1615043
Session's developers dropped Signal's Perfect Forward Secrecy (PFS) and deniability
[0]security features. Personally I would not trust a product that drops an end-user security feature for the sake of making the developer's life easier[1].For those unaware, PFS protects your data/messages from future exploits and breaches. With PFS, each message's encryption is isolated, preventing compromise of current and past interactions
[2].A simple example to illustrate why PFS is beneficial. Lets assume any 3 letter agency is collecting all Signal/Session messages - on top of the tons of data they're already capturing. The great thing is that your messages are encrypted, they can't see anything - YAY - but they're storing them basically forever.
Two ways they may be able to compromise your privacy and view ALL your messages:
A flaw is discovered that allows them to crack/brute force the encryption in weeks instead of years/decades/eternity. If you were using Session, because you use the same key for every message, they now have access to everything you've ever said. If you were using Signal, they have access to that one message and need to spend considerable resources trying to crack every other message.
Your phone is compromised and they take your encryption keys. If you were using Session, this again gives them access to your entire message history. If you were using Signal, because the keys are always rotating (known as ephemeral) they can only use them to unlock the most recent received messages.
It's important to state that both cases above only really matter if you delete your messages after a certain time. Otherwise, yes, all they have to do is take your phone and get access to your entire message history - which is why ephemeral messaging (i.e. auto deleting messages after a certain time) is crucial if you suspect you may be targeted.
[0]https://getsession.org/blog/session-protocol-explained[1]https://getsession.org/blog/session-protocol-technical-information[2]https://www.signal.org/blog/advanced-ratcheting/