[TacticalCoder]

Speaking of physically immune schemes, I remember some protocol which relied on a gigantic amount of data present behind a link that was, on purpose, very low bandwidth (physically low bandwidth: not by software as in rate limitation. That was the whole point: the link was physically low bandwidth).

So the data was impossible to exfiltrate remotely: it simply wasn't physically possible to do remotely (it would be way too slow).

I forgot the name and what the data was used to protect/derive: maybe some authentication scheme?

Anyone knows what I could be talking about? I'm pretty sure I saw that posted here on HN in the past.

[gruez]

>I forgot the name and what the data was used to protect/derive: maybe some authentication scheme?

It's a variant of salted passwords, where the "salt" is a huge file that sits on a server somewhere. To validate any given password, it only requires accessing a few bytes that are deterministically but randomly determined. This isn't a problem when validating passwords, but if you're an attacker trying to exfiltrate the file (so you can run offline bruteforce attacks on it), the huge file becomes prohibitively expensive to exfiltrate.

[notarealllama]

The closest I can think of is ULF radio, which has two properties - extreme range and penetration, at the expense of extremely low bandwidth. My understanding is that it is used to communicate with underwater subs, but likely on the form of simple ascii or Morse code keywords.