I guess similarly you can carefully craft a poster with a QR code and put it on a wall in a room with two LED bulbs. The bulbs will have different color temperature and the decoding will be dependent on which bulb is lit.
Another idea would be a poster that's not quite flat: Each pixel that is different is slightly raised (pyramid shaped) and the sides of the pyramid is colored differently. So the QR code scans differently from different sides.
One of the dominant banks here in Tbilisi allows sharing of IBAN number as QR codes. In theory, the trick could be used to steal money, but in practice, there are many safeguards such as the banking app displaying the name of the beneficiary before completing the process.
Most likely, they have <1s bank transfers, too, like pretty much all of Asia. That way, if you pay someone with a QR code, they'll immediately get the notification that they received your payment. And if they don't, you immediately know that something went wrong.
Most scammers will try to avoid situations where you can punch them in the face. => If scams usually get notified before the perpetrator can run away, that will discourage scamming. => In practice, it might be "good enough" if you know immediately after sending money.
Another idea would be a poster that's not quite flat: Each pixel that is different is slightly raised (pyramid shaped) and the sides of the pyramid is colored differently. So the QR code scans differently from different sides.
One of the dominant banks here in Tbilisi allows sharing of IBAN number as QR codes. In theory, the trick could be used to steal money, but in practice, there are many safeguards such as the banking app displaying the name of the beneficiary before completing the process.