It's basically the same technology that's used at the register. You pick up a barcode scanner, you scan your items, and the scanner produces a hash of your item

It's basically the same technology that's used at the register. You pick up a barcode scanner, you scan your items, and the scanner produces a hash of your items that can be scanned at checkout to reproduce the list. Super simple technology. The store could gather how much time it took you to scan between items and in which order, but you can pay with cash if you're worried about personal privacy.