Quote from: statdude on April 15, 2019, 06:38:25 PM

Anyone know how and if these can be used WITHOUT the tangem app / support?

The transparent one is a special edition with unlocked features, where the white one have some limitations concerning the times that can be loaded/unloaded

I am not quite sure if they can be used without the tangem app. Your best bet is to contact tangem support and ask. Actually depends on what would you like to do with them (without the app).

Those cards are designed to act like physical bank notes (pass them around, without having to move BTC through the blockchain). The private key is stored inside the chip of the card (similar to the opendime), and you can only see the public key. You load those cards (once) with the denomination amount (i.e 0.01 BTC for the 0.01BTC card). Then you can physically handle them to someone (like real banknotes). When you tap the card to an NFC enabled device (through the app), there is an indication mentioning if the card is valid (green label) or invalid (red label) & also the amount that it is loaded with. You can load the card many times, even with more than 0.01BTC, and the status will still remain valid. If you unload even a small amount from the card, then the card status changes to invalid. The card continues to work as normal, and you can load and unload it (up to the times limit). However, the red status is an indication that the "seal" was broken, and (even once) the card was unloaded (hence to warn you to check better for the loaded amount of the card).

I believe that they use proprietary technology for chip/software. Hence in order to unload it (for security reasons), you might need to do it only through their app (in order to transfer/unload an amount from the card to an addy, you have to keep the card for 2 minutes -without interruption- attached to the device). However, in order to view the balance, just a small tap is enough. I do not know if they have open sourced the API for reading the card balance and if by using an NFC tools app, you can just read the indications. (i.e. you are a merchant and you would like to check the balance/validity of the card, but do not want to rely on their app)

That's why (as I said to the beginning) your best bet is to ask them. I contacted them long ago, and they were very helpful in answering all my questions. if you have any other questions, just shoot

(I haven't tested them yet with an NFC reading app to get indications. only through the official app)

BTW, if you get a response, I would be very interesting to know that info as well. Feel free to post here or send me a PM Wink