Bitcoin Lightning Payment Cards

Some like to read, some like to watch tutorials which is why you will find a variety of documentation available here on how to write different sorts of payment-links to your Plebtag NTAG424. So lets first decide what to do

Create or update a Boltcard – for bigger amounts

Write a paylink to generate simple Voucher- or Tippingcards

Voucher cards in a batch – as give-away for an event or a conference

Create a Boltcard

While the simple LNURLw voucher work with nearly every wallet out there

sadly not all wallets support the boltcard service yet.

An easy way to create and run a Boltcard is with the BoltCard Wallet App. To run this self-sovereign youll need to also run a BoltCard Hub (similar to LNDhub) to genereate the keys and write the cards with it.

If you are not tech-savy please read on – there are more solutions that can also be set up non-custodian.

What you need:

  • a NXP NTAG424 card from us or any other supplier
  • an LNbits or BTCpay instance in clearnet*
  • opened on Android in chrome/chromium browser (to tap and import the UID of the tag. If youĀ“re on iOS you can read the UID from the Bolt Card Writer App)
  • install the boltcard extension for your LNbits wallet resp. a Boltcard Factory on BTCpay
  • Install latest version of the Bolt Card Writer App from the Play-Store or Apple-Store to write your keys to the tags once they have been generated by BTCpay or LNbits

The BTCpay process is described in the links above. For LNbits there are videos that help you guide you through the setup.

The beneath described process sets up the secure version of an NFC Tag that communicates to the Boltcard webservice of LNbits to authenticate each single request before allowing a payment. You can also find a textual description of the process here alternatively.

šŸšØšŸšØšŸšØ The keys you generate are needed when you want to rewrite your card in the future,

DO NOT DELETE THOSE KEYS without a backup šŸšØšŸšØšŸšØ

A .json file will be force-downloaded in the end of the writing process with which you could recover those wallets. Do not play with šŸ”„ deleting the keys, card or even the wallet because you have that file. IIf you delete the wallet or the card or if you regenerate your keys, your old setup will be gone from the database and without backup you will not be able to rewrite your card ever again.

If you want to gift a card not with a plain voucherlink (recommended because of easier rewrite) but with a Boltcard, please include the following data for the user to be able to make full use of your present.

Change a Boltcard

Got a prewritten Bolt Card and now you want to connect another wallet to it ? This is a bit tricky.

First you need to start deleting the old values ->where they were written<-. Means, if you have a CoinCorner Boltcard you will have to start the wiping process from there. If you have written a wallet to your tag with the LNbits or BTCpay boltcard extension you will also need the wipe keys of this card from there to be able to do so. If you have deleted the card in the extension without making a key-backup the card is bricked a nice bookmark.

If putting in the old keys fails x times you will have to succeed the same amount of taps with the right ones before it will be unlocked again (error 91AD). You can find more info on that in this document from NXP chapter 7.4.

To make all this easier LNbits offers a QR-Code to do so. Start the video fromon 2:40. SUper nerdy experts can do this manually according to this written tutorial using the NXP-Write Tool. Everyone else will need the BoltCard App to delete the old values.

If you donĀ“t have the wipe keys for your old setup there is no way of writing to those tags ever again. Remember that this is a security feature of NTAG424 cards and has nothing to do with the boltcard-service or -app.

Simple printed tipping cards, voucher or contest

If you want to give away cards on a conference or as voucher we suggest using a NTAG424 but write a normal lnurl to it (LNbits extension “withdraw” instead of the “Boltcards” extension. This way users can easily rewrite it with their own safer version when the voucher funds are redeemed. We can not recommend to use a plain lnurlw (not BoltcardI) as a debit card.

This use case does not require high security because the link might not be used for long like e.g. as long as your event goes or as a present that will be redeemed soon. The missing security features also lets you use Tags fromon NTAG21*.

Within this process we will write a simple LNURLw to the tag without any further security features. But for events it is the most common give-away voucher and can also be used for event games where some out of all cards have a winning-option. If you are into tinkering you can e.g. turn something on (lights, music, a confetti machine,..) when a certain card is used.

You can also find an english textual description on how to write those here. The longer process including putting your LNbits into clearnet is explained in the following german video. Just set it to auto-translate to translate into your language. If your LNbits already is in clearnet you can of course scroll forward.

or if you speak spanish Bitmaker also made a video on the writing process

arbadacarba made a video on how to upload a nice custom design (templates in the shownotes) for gifting such cards.

Voucher cards in a batch

After some downtime the machine is working again šŸ¤“šŸ„³ šŸ«”
With that tool you can set up an amount of wallets each with lnurlw / lnurlp / lndhub in a batch and write those to NFC tags / print stickers for them in one workflow. On every choice youll get the resp configuration options below.
Tags can be any >NTAG215.
** Note that LNURLw is just suitable for vouchers e.g. as a give-away for an event. Sort-of-debitcards should still be done with the boltcard-extension on a NTAG424!
Handle amount of requests with care #killswitch ā˜ ļø


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