Comment by upofadown

Their existing post quantum encryption didn't do post compromise security (PCS) against quantum attackers. This new one does.

I am excited to finally know what they mean by PCS after reading this article. It means that the session keys from their key agreement scheme (n ratchet) are generated new so an attacker doesn't get them again after a fairly specific sort of compromise. So from that I get that the off the record (OTR) protocol also has PCS. Which is a bit disappointing, I thought that they had come up with some new concept.

This key agreement doesn't happen that often. So a user isn't going to notice any slowness even if it was significantly slower.