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Show HN: ShadowCat – file transfer through QR Codes in a Browser

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Re: Show HN: ShadowCat – file transfer through QR Codes in a Browser

#21

Post by [deleted] »

MattCruikshank wrote: post #19
skinfaxi wrote: post #16

Earlier quoted context omitted.

> I have a device with a camera and a touch-screen that only uses capacitive charging. I type a message. Bytes are encrypted. I hit send. QR codes flash on my screen. I use my PC or my normal phone to receive the encrypted bytes, and transmit them to you. You have the same device. Why do you need a separate device for this and not just an airgapped computer?

Me, in my life, I have a PC that's connected to the internet. I have a phone that's connected to the internet. I want another device, which I imagine to be a Pi or Esp32 or something with a camera and a touchscreen display, and capacitive charging. After I program it and give it the public/private keypair and the OTP, I imagine physically breaking off a USB port, or sealing one with some hardening resin. I don't want…

[deleted]

Re: Show HN: ShadowCat – file transfer through QR Codes in a Browser

#22

Post by bensyverson »

hoansdz wrote: post #7

I once heard someone create a QR code scanner to retrieve gigabytes of data, but the biggest problem is that cameras aren't powerful enough to handle it all. Essentially, the QR code needs to be downloaded to the device for loading; relying on the camera to retrieve it is very difficult. Am I wrong about this project? What's your solution?

I've done a POC with the native QR reading code on iOS. The short answer is: it's not a problem at all, and you can drive very large QR codes for more efficient transfer.

Re: Show HN: ShadowCat – file transfer through QR Codes in a Browser

#23

Post by deletedie »

hootz wrote: post #20
skinfaxi wrote: post #18

Earlier quoted context omitted.

Did you explore using frequencies outside the range of human hearing?

No, but that's a cool idea. I think the main problem is that consumer hardware usually gets kinda inconsistent outside our hearing range.

Apple uses this approach when pairing some devices for verification e.g. setting up HomePods using an iPhone

Re: Show HN: ShadowCat – file transfer through QR Codes in a Browser

#24

Post by divan »

This method of animated QR data transfer is quite efficient with fountain codes. I had PoC implementation back in the day - Txqr [1] [2]

[1] https://divan.dev/posts/animatedqr/

[2] https://divan.dev/posts/fountaincodes/

Recently I rewrote it in Dart/Flutter and finally implemented RaptorQ codes (way more efficient than Luby used in original Txqr). Testing it internally now, prepareing Appstores/GooglePlay/Web deployment and new article.

Re: Show HN: ShadowCat – file transfer through QR Codes in a Browser

#25

Post by skeptic_ai »

thedougd wrote: post #13

I've done this exact approach before. It's a good way to exfiltrate data. Post the software on GitHub pages, or a popular CDN that co-hosts other shared libraries and you've got a very difficult to block method. Really goes to show that it's very difficult to stop a motivated and informed actor.

Npm install qr-made-up-name Can show qr in console. How do you stop that?

Re: Show HN: ShadowCat – file transfer through QR Codes in a Browser

#28

Post by HanClinto »

unprovable wrote: post #2

Single page file transfer using QR Codes and a browser. Sending device loads a file into the page, gets chunked. Receiver gets all the chunks through a camera, tosses lightly and reassembles, CRC to garnish. Designed to push data from an old phone that had broken comms after it took a swimming lesson in a coffee mug, it's been quite handy.

If the phone had broken comms, how did you get the code onto the phone to run?

Re: Show HN: ShadowCat – file transfer through QR Codes in a Browser

#29

Post by reaperducer »

MattCruikshank wrote: post #11

I've wanted to use this for an air-gapped communication device. I have a device with a camera and a touch-screen that only uses capacitive charging. I type a message. Bytes are encrypted. I hit send. QR codes flash on my screen. I use my PC or my normal phone to receive the encrypted bytes, and transmit them to you. You have the same device. You have your PC or phone flash encrypted QR codes. You use your device to r…

I have a device with a camera and a touch-screen that only uses capacitive charging. I type a message. Bytes are encrypted. I hit send. QR codes flash on my screen. I use my PC or my normal phone to receive the encrypted bytes, and transmit them to you. You have the same device. You have your PC or phone flash encrypted QR codes. You use your device to receive, and then decrypt.

Congratulations. You just invented IrDA: https://en.wikipedia.org/wiki/IrDA

Re: Show HN: ShadowCat – file transfer through QR Codes in a Browser

#30

Post by reaperducer »

skinfaxi wrote: post #18
hootz wrote: post #14

Earlier quoted context omitted.

I guess lmao, but much more rudimentary, less reliable and with loads of issues, as it had to blast piercing sounds through a speaker and then capture those with a microphone. But it was pretty cool when it worked!

Did you explore using frequencies outside the range of human hearing?

Did you explore using frequencies outside the range of human hearing?

Amazon had modems very much like this in its little buttons that you could stick to your refrigerator and automatically order different items. When setting up the device, you could only hear the little clicks as it turned on and off.

I loved the technology. Hated that the prices changed all the time and you never knew what price you were going to pay ahead of time.

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