201 sats \ 6 replies \ @supertestnet 20 Jun \ parent \ on: Nerd alert: ecash via sound? bitcoin
@cascdr and @BlueSlime and I made a project last year called Satoshi Jump which can convert any piece of text into DTMF tones (the ones used to transmit phone digits) and then send them to another computer via sound. In theory you can use this to transmit bitcoin transactions and LN transactions via sound, but we didn't do that part, we just transmitted short text messages.
here's the demo video:
Summary:
- The team, Satoshi Jump, aimed to tackle the problem of broadcasting Bitcoin transactions over the radio without internet to widen the network reach and enhance censorship resistance.
- They used dual tone technology and digital signal processing in a browser-based offline module to transmit and interpret hexadecimal codes.
- The team demonstrated their solution by sending words over the airwaves using tones and showcased the potential for making Bitcoin transactions in areas with limited internet access.
- Future work includes improving error correction, increasing transmission speed, and exploring walkie-talkie radio stacks and phone integration for wider accessibility.
TLDR:
- Team Satoshi Jump developed a solution to broadcast Bitcoin transactions over the radio without internet.
- They used dual tone technology and digital signal processing in a browser-based module.
- The team demonstrated the solution by sending words over the airwaves using tones.
- Future work includes improving error correction, increasing transmission speed, and exploring phone integration for wider accessibility.
- The project aims to enhance Bitcoin network reach and censorship resistance.
Conclusion:
The video showcased the innovative approach of Satoshi Jump in enabling Bitcoin transactions over the radio without internet, highlighting the potential for expanding the network's reach and enhancing censorship resistance. Their future work focuses on improving the solution for faster and more reliable transmission, as well as exploring additional integrations for wider accessibility.
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Would this be possible with a sound that is not possible to hear for humans? e.g. in a specific frequency? Then it could be used so pay contactless between two devices... :)
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I think it's possible if the two devices (1) are close to one another (2) have the volume turned up (3) use a "regular" speaker + microphone (4) the background isn't very noisy
I doubt it is feasible via walkie talkies. I assume their range of transmissible sounds doesn't include much outside the range of human hearing, plus they transmit lots of static, interference, and environmental sounds which would probably ruin the effect. It's probably not even feasible in a setting like paying for coffee at a starbucks due to too many variables listed above. Humans are bad at following procedures precisely unless they are conscious of the requisite conditions and why they are needed, and I think #1 and #2 would trip normal people up.
E.g. I suspect people would try to pay with headphones plugged in and then not understand why it's not working. Even without headphones, some users would probably turn the volume down if the payment app turned it up without them understanding why. And you can't rely on "just telling them why" because people don't read what their apps tell them, they just complain when they don't work the way they wish things worked.
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It's possible. Phone transducers can send/receive up to around 20kHz.
Most adult humans can't hear beyond about 15kHz.
You'd need to keep in mind transmission distance which decreases with frequency which can be either a feature or a bug.
You can apply the same principles as Satoshi Jump using DTMF + The Goertzel Algorithm for tone detection. DM one of us if you'd like to learn more.
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My thinking on this question: I don't know the answer, but my gut says it's possible (though not too practical). While futzing with things like psk31, I've noticed that the sound level, even the audible sounds, the volume does not have to be very high at all if the devices are very close. For example, while setting up the 21 sat transfer audio file in the link up above, I used normal earbuds dangling over my laptops mic. I did that because the audio was too annoying my wife would have strangled me. I have rather poor hearing, but I could not audibly hear the sounds even though the data was being transferred earbud-->mic-->Fldigi to decode.
As far as outside the range of normal hearing thresholds, that's probably something for a ham radio person to answer. User bitpunkfm suggested waver (ggwave) over on nostr. I'd never heard of it, but it might be doing what you're describing with "ultrasonic" messages. See youtube vid, the first couple of tx you can hear, the ultrasonic message is at about the 33 second mark.
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