> the session key cannot be recovered
Of course it can, but only for that specific session.
No, my GP is correct: if the server's RSA private key is compromised it does not allow decryption of any previously-recorded sessions.
You would need to compromise the _ephemeral session key_ which is difficult because it is discarded by both parties when the session is closed.
Compromising the RSA key backing the certificate allows _future_ impersonations of the server, which is a different attack altogether.
I wish for syncoid to add this feature. I want it to only copy snapshots to the backup server. The server then deletes old snapshots. At the moment it requires delete permissions.
You'll need to add the --no-elevate-permissions flag to your syncoid job.