Hacker News Reader

Comment by MaxBarraclough | Hacker News Reader

Is it legal to use crypto with ham transmissions? I was the under the impression that was generally forbidden.

Section 97.113(a)(4) of the Amateur Service rules prohibits the transmission of “effectively encrypted or encoded messages, including messages that cannot be readily decoded over-the-air for true meaning.”

What _exactly_ that means is, of course, up for debate. Some say you can use encryption as long as the key is publicly available and obvious (i.e. my key is "password"). There's been a bunch of stuff happening in the last year around Winlink. Devil's in the details.

What's the difference between encrypted messages and broadcasting random noise? Who could actually prove otherwise without the key?

Well, broadcasting random noise would be illegal, so...

Every transmission whether data or voice has random noise in it.

We both have a shared key, I send you a cat picture over ham radio with the message encoded in the least significant bit of each pixel.

How exactly is that going to be detected? The picture looks virtually the same as the original.

The point isn’t whether it’s detectable or not.

Not everything is about whether or not you get caught.

Why would you need to prove the difference between noise or encryption?

If they claim is not encrypted it's just noise, prosecute them for broadcasting noise.

If they claim it's not noise it's just encrypted, prosecute them for broadcasting an encrypted signal.

What do you think the practical difference in outcome is?

The practical difference is you can send any sort of data with packet radio, how are they actually going to prove you've hidden an encrypted message inside that without the key (preferably symmetric)?

This isn’t how the law works. It’s like saying ‘why is murder illegal when I can sometimes get away with it.’

There are exceptions that allow for use of encryption to authenticate remote control of satellites and such. But generally speaking, it violates the rules to obscure the content of a message.

It's absolutely illegal, unless it's somehow an emergency that requires it. Don't let anyone say otherwise, there are some crazies who think it's legal.

Yes, as long as the key is available. For instance, we use WPA keys for our HAMnet microwave links, but using a well-known key that's publicly known.

D-Star and PACTOR are proprietary, undocumented algorithms but you're allowed to use them because devices implementing them are commercially available.

I guess there should be a sound technical reason for choosing to encrypt with a well known key vs transmitting cleartext, but I fail to imagine it.

What's the advantage of doing it?

Our links are essentially standard 5 GHz wifi, but on licensed bands with higher tx power, and we don't want random people to connect to them. A WPA key mitigates that without breaking any regulations.

Mainly a mitigation against curious people with Ubiquiti equipment, which makes it way too easy to disable country restrictions and find and connect to our links in licensed bands :-)

So if they don’t know the key or where to find it, how is that “publicly known”?

You can easily find it on a public website if you know what you're looking for. It's only meant to deter people who click the "Scan" button on their equipment.

Well depending on what is broadcast, it might have a regular structure and perhaps there's some reason you'd want to randomize the broadcast signal. Maybe some highly specific noise in the environment that happens to resonate with the signal structure?

Alternatively there might be protocols which have mandatory encryption as part of their specification. Or you might be using a combined encryption-authentication mode, but only for the purpose of authentication on ham radio.

Those are all a bit of a stretch though.

My own view - legal to use to authenticate? Ie callsigns etc. not legal to use if it obscures message

Authentication is not encryption. Authentication is absolutely allowed, provided that it doesn't obscure anything.

Encoding is not encryption. Do you consider Morse code or Base 64 to be crypto?

Both have public documentation sufficient to decode a message without applying any secret information, so no.

The article states that The protocol allows for encryption.

Reply on news.ycombinator.com