Comment by miki123211

This makes me wonder why we aren't using pre-shared keys as one extra layer of defense.

The idea would be to use an existing connection (established via normal TLS) to agree upon and exchange a pre-shared key. For subsequent connections, that key would be incorporated as one extra input to the key derivation function, and a new key would be derived.

This would make TLS more secure against adversaries who can break asymmetric encryption (now or later) and monitor some of your communications, but who do not have access to all of your communications. If you managed to get on an unmonitored network even once (foreign hotel WiFi, coffee shop without a wiretap), and securely establish a PSK there, all future interactions would be inaccessible to an adversary who can't break symmetric crypto.