alt Hacker NewsI agree port knocking is a direct violation of Kerckhoff's principle. However, the proposed solution has non-discoverability from unauthorized sources which isn't necessarily in the threat model of OpenSSH or general cryptography. I do feel like this is potentially a desirable trait. I elaborated a bit more here[0], but I'm curious if you have any grander thoughts on how this could be approached
If you want that, I'd personally suggest wireguard. Bind sshd to the wg interface and it'll be invisible.