Suppose I have to confirm a transaction [ not bitcoin or any other cryptocurrency ]. I have been building a project which has a barcode that when scanned allows the user to pay tokens. I have been looking for creative ways to secure the barcode to not leave specified premises without the payment confirmed.'

Note: USE OF IOT DEVICES ARE ALLOWED

However, are there any other creative ways to confirm the transaction?

IOT devices should be cheap enough for industrial use.

USE OF CRYPTOGRAPHY TO CONFIRM THE PAYMENT IS WHAT THE WHOLE CONCEPT IS ABOUT without getting the customer to steal the barcode out of the permitted premises range.

Help is appreciated. thanks