WoodScientist@sh.itjust.works 1 week ago
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. 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.
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 trigger the bombs safely.
https://en…wikipedia.org/wiki/S%C3%A4kkij%C3%A4rven_polkka
to anyone else listening, it would simply sound like a song or other audio track being played.
I haven’t seen it mentioned yet, but legally, you can’t transmit music over ham radio either.
SnotFlickerman@lemmy.blahaj.zone 1 week ago
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.
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.
AwesomeLowlander@sh.itjust.works 1 week ago
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.
Deestan@lemmy.world 1 week ago
It’s fine, but you need to have an error correction layer.
Digital-over-analog methods like QR codes or modems are some examples.
AwesomeLowlander@sh.itjust.works 1 week ago
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.
evasive_chimpanzee@lemmy.world 1 week ago
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
AwesomeLowlander@sh.itjust.works 1 week ago
Sounds more like you’re using codewords and phrases at that point? Or do you mean something different?
nondescripthandle@lemmy.dbzer0.com 1 week ago
Its not too hard to set up most modern trancievers for digital modes, I think the harder part would be making the mode itself.