Hello,

I'm new here. I have been in and out of Bitcoin and some altcoins since 2017.

I was having coffee with a friend yesterday and we were trying to think about how mainstream adoption could be made easier. Not everyone has access to a smartphone and internet.

Recently, I saw a chap post online about bitcoin denominated cards that have the private key embedded in them. (My concern is, how can you know the private key without opening the card, and even then, how can you know someone else does not also have a copy?

Could you reveal part of the private key (so that you have some authenticity) then have some kind of gadget that sends a message on chain to keep a record that the card has been opened, or something like that?

Is it possible to have bitcoin notes in that case, with the denomination (e.g 50 sats), the private and the public key, printed on the note, and each note have it's own wallet ID?

One barrier I can immediately think of, is that there would be nothing to stop 2, or even 100 identical notes with identical private keys floating in circulation, which means we fail the double spend problem. However, is there a way in which we could have bitcoin notes? How could we facilitate the creation of such notes and guard against forgery.

The fewer barriers for users, the better.

Thoughts?