[Nursie]

> A) allow for secure payments without giving away something like a bank account # or debit card number

We have a whole bunch of these systems, like Open Banking payments in the UK, Pix in Brazil, and to a lesser extent stuff like Apple/Amazon pay and other payment proxies which don't require you to expose account numbers to merchants. Physical credit-card transactions work this way too, as the chips have built-in cryptographic processors.

> such as people at a bank just deciding to initiate an account with one million?

This is not a problem people really have. Having a limited quantity of your means of exchange is not a desirable quality in a currency.

[ilaksh]

Credit card transactions may at some point involve cryptography, but at the bottom is the credit card number, and that can still be exposed.

Cryptocurrencies don't necessarily have to operate on an (effectively) fixed supply, and actually if you are concerned about modifying the supply frequently it is possible to design a cryptocurrency that gives you much better control over that.

[Nursie]

> Credit card transactions may at some point involve cryptography, but at the bottom is the credit card number, and that can still be exposed.

That's not really "at the bottom of things", for physical, customer-present transactions which I was talking about there. At the bottom of things are private keys stored on the card, which sign the transaction. Exposing the credit card number gets you no more than having someone's cryptocurrency wallet address, in fact a lot less as you can't look up their balance. The idea that credit card transactions are simply the handing over of a number, that a merchant can then do with whatever they like, is very outdated, though I guess still makes sense in countries that haven't moved on from magnetic strips.

Yes, plugging in your card number online to buy things is still distressingly popular for various reasons, I agree we should definitely get rid of it. And we can! Either by reforming the credit card payment process in the sort of way Apple Pay online payments and Paypal already have (though they still use the numbers themselves, it's true), or by ditching cards entirely and going with things like open banking payments and pix, which tend to have OAuth under the covers (among other measures) that don't involve 'card' infrastructure at all.

The question was how you design a system from the ground up that will "allow for secure payments without giving away something like a bank account # or debit card number". Well, I would use these sorts of technologies (that already exist and are in widespread use), rather than a blockchain.

[ilaksh]

It's amazing how well you seem to understand some of this stuff but aren't able to apply that knowledge in a holistic way.

[Nursie]

It's amazing how superior you've let yourself feel while not addressing anything.

Was I supposed to have a revelation that cryptocurrency is the answer, in some sort of holistic come-to-jesus moment? Sorry, no, cryptocurrency is still a crapfest.