Hi all,
There are some bitcoin use-cases where I can't find a solution other than having some addendum to BIP 21.
This post is just to see if I'm missing something and whether these use cases merit a BIP 21 change or best practice addendum.
Use cases:- merchant prints a QR code on his invoice with the exact amount in EUR/USD/...
- a club bar wants to print 3 QR codes for its 3 kinds of drinks (beer,cola,water=2 euro, wine=3 euro, ...)
Note: these use cases can also be solved by a link on the invoice and a smartphone/pc in the club bar, but sometimes a printed QR is more convenient.
Proposal:Add these elements to the query component: fiatvalue, fiatcurr, exchangeprovider
=> can be done without changing BIP 21 by using req-fiatvalue, req-fiatcurr, req-exchangeprovider
Example:The merchant can print a QR code with his bitcoin address, fiatvalue=50.35, fiatcurr=EUR, exchangeprovider=bitcoinaverage.com
His client can scan this the same day or many weeks later, and if his/her wallet has support it will calculate the required bitcoin amount using the bitcoinaverage.com exchange price.
On exchangeproviders:The exchangeprovider might be considered redundant but this could be handy for payment processors so they can use their own.
To prevent arbitrary urls a list of accepted providers might be added to the BIP, or managed seperately as is done by satoshilabs for BIP 44.
Let me know what you think and please be kind