In some countries (such as the USA), sending encrypted communications via Amateur Radio is illegal, but how likely will the government actually enforce it, and how severe would the consequences be?
In some countries (such as the USA), sending encrypted communications via Amateur Radio is illegal, but how likely will the government actually enforce it, and how severe would the consequences be?
So... I found out a way to send encrypted messages using amateur radio.
There is an app called Rattlegram that lets you convert a string of text into soundwaves that plays though your phone's speaker. If I just use an app like Secure Space Encryptor (SSE) to encrypt a text, then copy-paste it to the Rattlegram app, then transmit that over radio, then using the same app to record the sound and reverse the process on the other end. Voila! Encrypted long(ish) range communications without a centralized server!
But I looked it up and apparantly its illegal to encrypt communications over the amateur radio bands. What are the odds of actually getting in trouble? 🤔
(To the FCC agents reading this: this is just a hypothetical, a thought experiment, I'm totally not gonna do this 😉)
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What if instead you hid an encrypted signal within an otherwise perfectly legible audio signal? Imagine a song being played. To the ear the song seems perfectly normal. But, unbeknownst to a casual listener, there is an encrypted signal embedded within the audio signal. For example, data could be embedded within a song by ever-so-slightly raising or lowering the pitch of a song multiple times per second. Then if you had a copy of the original file, software could compare the original file to the song transmitted over the radio. The locations where the pitch rose or fell could be noted, and the data could be retrieved. You could send encrypted data without anyone realizing you're sending encrypted data. To anyone else listening, it would simply sound like a song or other audio track being played.
Actually, this idea has some merit, because it already has examples in other mediums. It's technically referred to as "steganography."
A common example with computers is hiding text, files, or applications within an image file.
https://github.com/7thSamurai/steganography
In the example for how to use this simple Image Steganography tool, the user hides a ZIP files with the entire contents of the book Dr. Jekyll & Mr. Hyde into the example image.
I don't see why something similar couldn't be achieved with audio.
In fact, here's an article on some basic audio steganography methods.
Not an expert, but I'm not sure steganography would be compatible with analog lossy data transmission methods like ham radio. The examples you linked relate to digital lossless audio, where it's easy to hide the data in individual bits.
There's a whole bunch of different steganographic methods. You wouldn't necessarily have to apply them to audio signals, you could apply them to the text itself. It's certainly trickier, so you would want to keep the plain text very short so your ciphertext doesn't get too long or weird
Sounds more like you're using codewords and phrases at that point? Or do you mean something different?
I'm not clever enough to come up with a good example on the spot, but you could have something along the lines of a scheme where the word selection corresponds to a not-obvious code. For example, if you wanted to secretly send the word "hello", and you've previously given your receiver a code word "apple":
Hello > 7 4 11 11 14 Apple > 0 15 15 11 4
Adding the code word to the secret message, you'd get:
7 19 0 22 18 > H T A W S
Then your message could be something like:
How are you doing? Today, I went to the store. Avocados were on sale. When do you want to meet up? Saturday looks good for me.
There are definitely way better methods to do the encoding part, and probably also better ways of doing the concealment part.
Yeah. At that point I think it's no longer considered steganography. It's really interesting though all the stuff they did during the cold war to get past surveillance.
Its not too hard to set up most modern trancievers for digital modes, I think the harder part would be making the mode itself.
It's fine, but you need to have an error correction layer.
Digital-over-analog methods like QR codes or modems are some examples.
I mean, it's certainly possible. But given that you're trying to keep the audio as legible speech, the bandwidth would probably be horrendous.
Yeah for sure! I'd be happy to encode a single word in a minute of audio.
This was used in the war between Russia and Finland in 1941. Without software though.
Russian had placed bombs in a city in Finland and the bombs could be triggered by a combination of frequencies broadcast on radio.
The Finnish engineers figured it out and drove a car around the city broadcasting a song that would scramble the frequencies.