[codetrotter]

Port knocking appeals to me because of how few bytes you have to send. But a system I’ve been thinking of (and surely a bunch of people before me) goes like this:

Instead of knocking on ports, send actual HTTP requests to different paths. Over TLS or just plain HTTP.

So where you’d port knock a sequence of ports here instead you send GET requests to some different, publicly known paths

GET /index.htm

GET /about_us.htm

GET /about_us.htm

GET /index.htm

GET /about_us.htm

GET /products.htm

You get the idea.

And now then the challenge is that if you’re on a network that does HTTP caching, it would interfere with this.

But we already have the well known cache-busting technique for that right, so

GET /css/main.css?ver=64729929

GET /js/bundle.js?ver=947367292

GET /js/bundle.js?ver=7483939

And so on. And version is for example current Unix time and is actually ignored in terms of “knocking”. Only the path matters.