We should figure out how exactly to do this and consider documenting it on the site, according to Matthew it should be possible to set the session duration to 1, possibly with a custom m.room.encryption state upon room creation? I also just found out that it doesn’t even seem like Matrix.org knows whether this is possible in existing rooms:
The other thing we should probably document is the default session length. I read it was 100 messages but I’m not totally sure, but that would mean that Matrix provides forward secrecy, just in batches of 100 messages instead of per-message, which is still probably better than alternatives which lack forward secrecy in any form.
Not sure if it makes sense to document this when it all sounds very experimental. It may create a false sense of security. I would refrain from it unless someone who actually has the authority and knowledge of the cryptography to say something about this has commented on this.
I think it might be useful to include an explanation on the site about PFS on Element and Matrix, since it can be a bit confusing. This explanation I was given on the PrivacyGuides room by @jonah was particularly helpful:
