For more about LNBits extensions check this tutorial
This extension allows you to link your Bolt Card on a NXP NTAG424 DNA tag with a LNbits hub that generated new links on each tab which allows a better privacy and security than a static LNURLw that you can also write to a NFC tag (fromon NTAG 213) in the withdraw-extension e.g. for one-time usage as a gift-card.
Disclaimer: Use this only if you either know what you are doing or are a reckless lightning pioneer. Only you are responsible for all your sats, cards and other devices. Always backup all your card keys!
For the easy way you need:
If you want to gift a Boltcard, make sure to include the following data in your present, so that the user is able to make full use of it.
Always backup all keys that you're trying to write on the card. Without them you may not be able to change them in the future!
Updated for v0.1.9
Since v0.1.2 of Boltcard NFC Card Creator it is possible not only to reset the keys but also to disable the SUN function and do the complete erase so the card can be used again as a static tag (or set as a new Bolt Card, ofc).
If you somehow find yourself in some non-standard state (for instance only k3 and k4 remains filled after previous unsuccessful reset), then you need to edit the key fields manually (for instance leave k0-k2 to zeroes and provide the right k3 and k4).
A technology called Secure Unique NFC is utilized in this workflow.
Up to five 16-byte keys can be stored on the card, numbered from 00 to 04. In the empty state they all should be set to zeros (00000000000000000000000000000000). For this extension only two keys need to be set, but for the security reasons all five keys should be changed from default (empty) state. The keys directly needed by this extension are:
One for encrypting the card UID and the counter (p parameter), let's called it meta key, key #01 or K1.
One for calculating CMAC (c parameter), let's called it file key, key #02 or K2.
The key #00, K0 (also know as auth key) is used as authentification key. It is not directly needed by this extension, but should be filled in order to write the keys in cooperation with Boltcard NFC Card Creator. In this case also K3 is set to same value as K1 and K4 as K2, so all keys are changed from default values. Keep that in your mind in case you ever need to reset the keys manually.
There's also a more advanced guide to set cards up manually with a card reader connected to your computer. Writing can also be done (without setting the keys) via the TagWriter app by NXP on Android.
The URI should be lnurlw://YOUR_LNBITS_DOMAIN/boltcards/api/v1/scan/{YOUR_card_external_id}?p=00000000000000000000000000000000&c=0000000000000000
Then fill up the card parameters in the extension. Card Auth key (K0) can be filled in the extension just for the record. Initical counter can be 0.
lnurlw://YOUR_LNBITS_DOMAIN/boltcards/api/v1/scan/{YOUR_card_external_id}?p=00000000000000000000000000000000&c=0000000000000000This app afaik cannot change the keys. If you cannot change them any other way, leave them empty in the extension dialog and remember you're not secured. Card Auth key (K0) can be omitted anyway. Initical counter can be 0.