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Bitchat – A decentralized messaging app that works over Bluetooth mesh networks

(github.com)
778 points ananddtyagi | 15 comments | 07 Jul 25 00:05 UTC | HN request time: 1.181s | source | bottom
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moneywaters ◴[07 Jul 25 05:35 UTC] No.44487086[source]▶
I’ve been toying with a concept inspired by Apple’s Find My network: Imagine a decentralized, delay-tolerant messaging system where messages hop device-to-device (e.g., via Bluetooth, UWB, Wi-Fi Direct), similar to how “Find My” relays location via nearby iPhones.

Now add a twist: • Senders pay a small fee to send a message. • Relaying devices earn a micro-payment (could be tokens, sats, etc.) for carrying the message one hop further. • End-to-end encrypted, fully decentralized, optionally anonymous.

Basically, a “postal network” built on people’s phones, without needing a traditional internet connection. Works best in areas with patchy or no internet, or under censorship.

Obvious challenges: • Latency and reliability (it’s not real-time). • Abuse/spam prevention. • Power consumption and user opt-in. • Viable incentive structures.

What do you think? Is this viable? Any real-world use cases where this might be actually useful — or is it just a neat academic toy?

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jacobgkau ◴[07 Jul 25 05:42 UTC] No.44487126[source]▶
> Works best in areas with patchy or no internet, or under censorship.

The biggest problem I immediately foresee is that this sounds backwards. It doesn't work best in areas with patchy or no internet, it works best in areas with lots of participating devices. It's most needed in areas with patchy or no internet, but those areas are likely to be the opposite of the areas with lots of participating devices.

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1. Dr4kn ◴[07 Jul 25 06:23 UTC] No.44487298[source]▶
If your country shuts off Internet access for demonstrations this would work great.
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2. xyzzy123 ◴[07 Jul 25 07:24 UTC] No.44487588[source]▶
I guess it depends on the authoritarian government, but a sufficiently powerful one will get the app taken down or get the bluetooth features it relies on disabled (like for airdrop in China) :/

I would say that the underlying issue is that people do not really "own" their devices and the corporations that do are vulnerable to (or complicit in) state coercion.

You cannot truly have freedom on a non-free device, you can just be small enough to not be worth taking action against yet.

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3. al_borland ◴[07 Jul 25 10:15 UTC] No.44488660[source]▶
But it would only really work well in a small area, such as a couple friends communicating at a demonstration, where there are a lot of people who may be motivated to participate in a particular area.

If there is a low density area between two people, a message could take a long time to show up. A message from NYC to LA is effectively relying on the messaging being cached on a phone in NYC, that person flying to LA, and then continuing the journey.

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4. synctext ◴[07 Jul 25 10:56 UTC] No.44488885[source]▶
Indeed! Advanced countries will and have blocked apps.

For a more extensive discussion on censorship resilient mesh networking, see IETF Internet Standard draft from 2012 [1]. After the Arab Spring there was global hope. Great to see revival of this topic today. Mesh networking is 1990s. The lesson from decades ago was that mesh networking can't be the killer use-case. Users need a reason to install this and allow it to drain the battery while looking for nearby nodes. Mesh networking never broke through the glass ceiling.

Blocking apps is real. Even Amazon killed a side-loaded app [2].

[1] https://www.ietf.org/archive/id/draft-pouwelse-censorfree-sc...

[2] https://torrentfreak.com/amazon-remote-disables-piracy-apps-...

5. ijustlovemath ◴[07 Jul 25 11:18 UTC] No.44489055[source]▶
Nation states can use the baseband radios to track/monitor you, so it's best to leave your phone at home. You can't disable or observe baseband from the higher level OS.
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6. teiferer ◴[07 Jul 25 14:37 UTC] No.44490831[source]▶
Though demonstration organizers could run around with QR codes making it easy for everybody to install the right app to communicate with each other during the demonstration. As long as people can side-load things on their phones, this should be possible without any way to stop it unless you deploy radio jammers. (Which is then the logical next step for police equipment in so minded states.)
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7. immibis ◴[07 Jul 25 15:22 UTC] No.44491322[source]▶
FWIW what people call "baseband" in the context of this particular security flaw is what everyone (including those people) call "cellular modem" in every other context.

On a Pinephone you can turn it off with a physical power switch.

If you really wanted to, on most other phones you could desolder it and throw it in the garbage. You'd need to already have custom firmware on the main CPU (or should I say "application processor" to fit in with the people who say "baseband processor") so it wouldn't crash or lock up when booting.

A little bit less destructive (in case you want to use your cellphone as a cellphone later) would be replacing the antenna with a dummy load.

8. al_borland ◴[07 Jul 25 16:58 UTC] No.44492306{3}[source]▶
People are supposed to scan a sketchy QR code to side load an app? That sounds like a security nightmare.

Those working against the demonstrators could send people out with QR code to infect the phones will malware for their own means.

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9. thenthenthen ◴[07 Jul 25 17:44 UTC] No.44492824[source]▶
Airdrop works fine in China, actually, if you leave it open you will be harassed by unwanted drops in public transport. E-sims are not allowed.
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10. ChicagoBoy11 ◴[07 Jul 25 17:58 UTC] No.44492993[source]▶
wait timeout... airdrop is disabled in china?!
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11. zikduruqe ◴[07 Jul 25 19:44 UTC] No.44493949[source]▶
That is what https://berty.tech is for.
12. xyzzy123 ◴[07 Jul 25 23:08 UTC] No.44495483{3}[source]▶
Was a bit more subtle than "disabled" really. See: https://www.engadget.com/apple-china-airdrop-limit-everyone-...

I think you could reasonably argue that the measure limits Airdrop spam.

13. xyzzy123 ◴[08 Jul 25 02:01 UTC] No.44496311{3}[source]▶
Yeah the change they made was to auto shut off airdrop after 10 mins. It's just that it happened to roll out in China around the same time that many apps were banned and protesters were reported as using airdrop to pass messages.

But I mostly agree - they rolled it out worldwide later on because once you reason it through, disabling it when it's not actively used turns out to be the better default.

14. torpid ◴[08 Jul 25 02:32 UTC] No.44496444[source]▶
If your country shuts off internet access they are probably going to jam bluetooth and wifi at any large demonstration, too.
15. thekid314 ◴[08 Jul 25 16:10 UTC] No.44501358[source]▶
Yeah, I used an older version of a bluetooth messaging app like this. We wish it had been available in the times of Tahrir Square, but it was actually helpfull onetime when my bus stopped at a rural Ethiopian bus stop, my girlfriend ran into the bathroom but was taking too long and I was able to warn her that the bus was getting ready to leave.

Wireless internet is getting better, but when you really need something like this, you really need it.