I appreciate the reference. I looked at that before starting and reference it in the blog post (but should probably include a direct link to the software rathe

I appreciate the reference. I looked at that before starting and reference it in the blog post (but should probably include a direct link to the software rather than the original concept post and article that include links). The similarities are they both use a single packet and they are both an improvement on port knocking. This is a simpler solution (pairing UDP with TOTP). No TCP connection is required. Making it ip address specific would prevent replay attacks (although even without address specific the replay would only be valid for ~30s). Another benefit is that a port scan will reveal no ports open (because it is a one-way UDP based protocol). fwknop is definitely a polished solution where this is just a proof of concept for the TOTP/UDP as a shared key knock. Thank you for the feedback! EDIT: I updated the post to include a direct link to fwknop rather than just links to the posts/articles about it.