See the sibling comment in this thread:

https://news.ycombinator.com/item?id=19903991

> I can't get my head around the fact that you are actually suggesting this. Do you want your bank to know that you buy 30-40 bottles of beer each week? Do you want them to know that you buy medicine for a terminal disease during your visit to discuss a family home loan?

Seems like the store could use your public key to encrypt the data it uploads to your bank, they get the full data, you decrypt it. It's then just using the current channels.

But, I imagine it's easier to have the store make a temporary xml/json file on their servers, give you the QR code to access it, then you can control the data flow from then.

It's important to me to minimize the amount of data leakage as much as I can as a matter of basic self-defense. As a result, I don't want anybody but the store I'm shopping at to have a list of exactly what I've purchased. It's nobody's business except mine and the store's.