>a lack of forward secrecy practically guarantees full decryption of the entire history of messages, for any ordinary participant in the system.
Can you elaborate?
Can you elaborate?
With email, because people quote when replying, you'll get the other side's messages too.
Like, the simple PGP-like system where sender encrypts message using recipient's public RSA key.
And of course it's not improved by switching from RSA to ECIES.
You need to ratchet the key, or double ratchet like Signal protocol.