Target Technology: Bitcoin
Target Audience: Bitcoin Developers
Blockchain Commons’ Animated QRs technology answers one simple question: how can I send a large data file, such as a PSBT, securely over an Airgap?
Animated QRs
Communication QR. The simple answer is Animated QRs. A standard QR is limited in size to 7089 numeric characters, 4296 alphanumeric characters, or 2953 bytes of binary data. Animated QRs allow infinite expansion beyond that size limit by fragmenting the data and then presenting the fragments as individual frames of an animated QR code.
Animated QRs are built using fountain codes, which allow for more efficient transmission and avoid the problem of missing a single frame and then having to cycle all the way back to that same frame again.
Though Animated QRs are built to support transmission across airgaps, innovative uses in other mediums are possible. For example, you could print out all the frames of an Animated QR on a piece of paper, and then read them back in from that, one at a time.
- For more, see Animated QRs
Uniform Resources (UR)
Communication Text. Animated QRs are built on Uniform Resources. These are a plan-text encoding method for binary data that’s self-describing and that can be stored efficiently in QR codes. The UR is also what supports the ability to fragment data.
- For more, see URs
Multipart Uniform Resources (MUR)
Multipart Communication Text. When a UR is fragmented it becomes a MUR. They allow for the encoding of larger data. Because of their use of fountain codes, they’re also great for transmitting over unreliable communication networks.
Our implementation guide for MURs is what you need to turn your data into UR fragments that you can then qr-encode. START HERE!
- For more, see MURs
- For more, see MUR Implementation Guide
Airgaps
Communication Gap. Animated QRs were built to allow transmission of PSBTs across airgaps. These are communication gaps built to protect your secrets. When you keep your seeds and private keys on a hardware wallet that doesn’t connect to the internet, that’s an airgap. QRs have become a preferred method for bridging that gap in part because they only allow transmission in one direction at a time (making attacks very difficult). But PSBTs were a problem: they’re an ideal use for airgaps because you can create your transaction on the internet, pass it through an airgap to the device holding your keys, sign it, and then pass it back through the airgap for transmission. The problem is that they’re usually too big to go in QR codes. Animated QRs offered the answer.
- For more, see Airgaps