Offline data sync from an old device to a new one. Many phone carriers provide for something similar in a QR code. My team has an app we developed that has a similar function because the private keys and all of the wallet items are exclusively offline. We show an qr code today. The issue we have hit lately is that the amount of data we have is more than a single code. Depending on the number of wallet items the users have. The animated QR is a good solution for this.

If someone is interested in how we got an amazingly small QR using base-91 and some other cool methods here is a good read with demo code

https://docs.google.com/document/d/1B7AJDVu5ei6c7ZuHRiTvQ_q8...

Why not just use a single code for bluetooth/wifi hand shaking? Wouldn't that be more efficient by any metric and almost as compatible? What device has a solid camera and no wireless communication?

Why not both? There is always the potential that there is an actual reason to upgrade - and borked motherboards where any such modules are damaged as a potential reason.

>Why not both?

User confusion and the fact that high quality camera tech and OCR aren't exactly cheap.

If this was more widespread or built into phones like QR code scanning is in the camera app, it could be an interesting way to share data with many people at once (something like a concert for example)

But I agree it's more interesting from a technical point of view over a practical one...

Bluetooth pairing isn't really as easy as this would be in theory (especially if we're talking about a situation where you want to send a message through a crowd of people -- so congestion will be pretty bad).

Bluetooth can be complex, finicky, and would add to the cost of a small device.

I could see this being used to share diagnostic information, certificates,condensed instruction manuals, &c.

Bluetooth is much cheaper than a screen or a camera.

A device would only need a camera to receive information, and yes, at the point you need bidirectional transfer, I'd concede that this isn't the best method.

However, adding a small lcd display allows the presentation of human readable data as well, and many devices already have screens on them.

(I always thought serial over TRS (headphone) cable would be an interesting option as well.)

Less robust and cheaper

Bluetooth LE is very robust. Much more so than a camera and screen.

Face-to-face key signing/exchange, or any other kind of in person secret sharing, perhaps?

BT/Wifi methods will broadcast data to anyone within radio range, but optical data exchange like this can take place under your coat, or using some easy means of protecting the transfer against 3rd party listeners.

A single QR code, or even a few words is sufficient for that.

Usually, yes. But cross-signed PGP keys, or certificates can easily exceed a single QRCode's capacity ...

It should have a multitude of applications where pairing is difficult, but physical presence of the device is necessary.

Some applications from the top of my head.

1. Access to buildings/restricted areas etc. can be made more secure, by using higher data content with animated codes, foregoing the requirement of the device having an internet connection. 2. Transfer data to a large crowd of people, say at a concert, etc. 3. Pairing of devices where one device cannot have bluetooth or other wireless hardware (due to power / security constraints)

Honestly, this is another channel of communication between devices and it's exciting.

from the top of my head, marketing gimmicks at some event, air gap jump and/or data exfiltration

> from the top of my head, marketing gimmicks at some event, air gap jump and/or data exfiltration

data distribution over normally visual broadcast channel (TV -> mobile device, billboards -> mobile)