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A small, instant top-up device to replace cash and enable anonymous payments

Image credit: https://metal-creditcard.com/2015/12/redundancy-emv-chip-now-available/; anyrgb.com

Povilas S
Povilas S Feb 09, 2022
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A small electronic device (around the size of a microchip card) that you can top up with a particular currency by simply touching with your contactless bank card or a smartphone through a banking app. You spend the money available on it the same way - touch it to any chip and pin reader and pay for a product/service.
The device has no Bluetooth, wifi, or remote connection of any sort apart from contactless loading and discharging of monetary value. It is not associated with your identity and keeps no record of transactions, only shows the amount of currency it currently contains.
  • Replace cash with something material and conceptually and functionally similar.
  • No need for bank accounts, electronic wallets, etc. to use the device and pay/get paid.
  • Maintain anonymity when paying/getting paid.
  • It is a solution to this problem.
How it works:
To enable top up with contactless bank cards, smartphones, smartwatches, etc. the device should work by a similar principle that chip and pin readers work, so it's pretty clear that a simple microchip (like on a credit card) won't do. It has to have the means to set the amount that will be loaded on it through contactless "touch". It also has to show you the amount currently loaded on it.
I think a card as thick as 2-4 standard microchip cards would do to hold the required electronics in place. You could go about different ways on how to set up the user interface, but I think the best would be to implement a small touch screen.
You'd activate the touch screen by entering your pin code. The screen shows you the amount of currency on the device. There is an "accept top-up" button. After pressing it a number keyboard shows up and you enter the exact amount to be loaded on the device, then press "confirm".
After that, the device is ready to accept contactless payment/top-up through various means. You can cancel this active mode by pressing another button. The device also cancels it automatically if it doesn't receive contactless transaction in due time.
Another interface option is to use a non-digital screen and a few buttons (a tiny physical keyboard). This might let the battery hold longer. The battery could be rechargeable or replaceable. If it was disposable then the device should warn the user well in advance to take the money out of it before the battery dies.
When you want to pay using the device, you don't have to do anything apart from touching it to the chip and pin reader (just like contactless bank card).
There could be separate devices for separate currencies (EUR, USD, Bitcoin, etc.) and I think it might be a good idea to set the limit amount that can be loaded on the device. That way it would be less of a detriment to lose the device. Similarly as banknotes have different monetary values, different devices could have different limit amounts to load on them. You'd use some for gathering and paying smaller sums and others for bigger transactions.
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General comments

Darko Savic
Darko Savic2 years ago
This sounds like a crypto hardware wallet. See if any of these fit
Even if the payment system is anonymous, vendors would be obliged by law to identify you before they accept your business
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Povilas S
Povilas S2 years ago
Darko Savic How do you load monetary value on a crypto hardware wallet? Or are they intended only for storing your security keys?
In any case, my idea is primarily about using non-crypto currencies with this, I'm not even sure how would you load crypto on such a device, just wrote it as a possibility. I should perhaps change the cover image.
The idea is to have a device which you can top up with money by any means of contactless payment (card, phone, smartwatch) simply by touching it like a chip and pin reader, except that it wouldn't connect to any external source, so it would basically be a smart top-up card. Once there's some money loaded on it, you pay with it the same way you'd pay with a contactless bank card.
I don't think such instant top-up cards exist. The closest to this is what J. Nikola mentioned in his comment under this contribution - an iPhone feature to be introduced soon letting you accept payments by tapping it with a credit card. However, having this in a smartphone compromises privacy and also is not suitable for people who don't have or don't want to use a smartphone.
Vendors are not obliged to identify you when you pay in cash at the store, so the idea is to make this an electronic cash equivalent. For security/crime prevention reasons it might be made so that you wouldn't be able to pay large sums with it. It could only contain, say, up to 100 $ at a time.
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jnikola2 years ago
Povilas S As I understood, you want to design a credit card that can function as a POS device, too? Cool! Crypto hardware wallets are physical storage for crypto, but I am not sure they can function following the "tap to pay" logic. Maybe Darko Savic knows something I don't.
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Darko Savic
Darko Savic2 years ago
Povilas S and J. Nikola a hardware wallet securely stores private keys with which the device signs bitcoin transactions. It can be embedded into a card-sized device and communicate with a POS terminal via NFC. You can come up with various ways (biometric, password, pattern, etc) with which only you give the card the green light to execute the transaction that the POS terminal has put together.
Bitcoin is always on the blockchain, in various wallet addresses. The wallet addresses are actually public keys, controlled by matching private keys that only the signing device/software knows. Your NFC-enabled card controls some of the wallets by having a matching private key. All the card does is sign transactions and return the data. You top up the wallets that the card controls by various means. For example, transfer money to a card-controlled wallet that is communicated to you via QR code, SMS, NFC, etc. The card can NFC the recipient wallet to another device (POS terminal, phone, etc). An independent device (like your phone app) can generate card-controlled recipient wallet addresses by knowing the right XPUB key. That key can't be used for anything else except generate recipient wallets that the card has the private keys for. The NFC card can share its Xpub key with any device that you want to give the ability to generate matching recipient wallet addresses.
The POS terminal shows you a request for payment. If you agree with it, you touch the terminal with the NFC-enabled hardware wallet (card) and authorize the transaction with whatever authorization mode the card uses (fingerprint, squeeze, whatever). The card NFC's a signed transaction back to the POS terminal which sends it on the blockchain or lightning network. If all is well, the transaction is complete and the POS terminal will know it instantly.
When you want to top up the card, you are actually topping up any of the (generated on the fly) bitcoin wallet addresses that the card controls. It can control an unlimited number of wallets. Both the wallets and the matching private keys are derived from the "master key" only the card knows. The XPUB is also derived from the master key. The XPUB can be shared with any additional device that needs to generate recipient wallet addresses for the card. The Bitcoin tech is ripe for anything:)
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Povilas S
Povilas S2 years ago
J. Nikola Yes, and not only that - the device (card) would not be connected to any virtual account (neither bank nor online wallet, nothing), the only place where the monetary value will be stored is in the card itself through inductively charging and discharging its's microchips. It also wouldn't be linked to your identity and would store no record of transactions done with it (just like is the case with cash now). It's designed for instant anonymous top-ups and payments.
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