I'm not really sure what you're trying to say.
The premise of cryptographically secure messaging is that you have an adversary recording all your message traffic.
Lack of forward secrecy implies, logically, that if your long-term secret is ever compromised, every message you've ever sent is recoverable from the adversary's archive.
The point of forward secrecy is to break that attack, so that your adversary needs your long-term secret at the time it was used to send a message; having it after the fact doesn't help.
I'm sometimes in the mood to write long posts and comments explaining this stuff, but today, on the bottom of this old thread, if you're trying to make a point about PGP vs. Signal and don't know how forward secrecy works, I'm probably the wrong person to have this conversation with.
The premise of cryptographically secure messaging is that you have an adversary recording all your message traffic.
Lack of forward secrecy implies, logically, that if your long-term secret is ever compromised, every message you've ever sent is recoverable from the adversary's archive.
The point of forward secrecy is to break that attack, so that your adversary needs your long-term secret at the time it was used to send a message; having it after the fact doesn't help.
I'm sometimes in the mood to write long posts and comments explaining this stuff, but today, on the bottom of this old thread, if you're trying to make a point about PGP vs. Signal and don't know how forward secrecy works, I'm probably the wrong person to have this conversation with.