[7952]

How do you know that it doesn't validate the discounted price against its database? Encrypting the barccode doesn't make it any more secure as you could simply swap with a completely different barcode. Encoding the price just makes it easier to develop handheld label printers.

[icebraining]

If they had verification against a database there would be no point in printing these in the first place, they could just get the discount info from the DB.

[lucaspiller]

Based upon my experiences working at Tesco, and the understanding I had of how their systems worked, I don't think any validation was done when I worked there (from 2004 until a few years ago). I can't see any reasons why they would have changed it as they still appear to use the same technology (Windows CE PDAs).

The main issue is they just didn't have the infrastructure to do this, remember this was before wifi was abundant. The PDAs which were used for printing discount labels and scanning out-of-stock products (and appear to still be used) synced over Bluetooth. So unless you could setup a Bluetooth network over the whole store it wouldn't have been feasible.

[ZoFreX]

Worth mentioning that most people trying this would probably go for the self-checkout, so you'd have to swap barcodes with something that weighed the same amount.