It was my hacking project over the holidays, I'll do a better explanation and demo in the following days.

Some things that I would like to improve:

- the radios have very low bandwidth. I refresh keysets on the launch, but that might not be the best idea, it can add a minute until launch. The UI is responsive though

- user interface is done in Kivy, so this should compile straight to APK and iOS app. That's why I based it on nutshell. Reticulum stack is pure python. The problem is that nutshell indirectly depends on sec256k1 and bitarray which are C libraries and they don't compile well using buildozer. It's a dependency of a dependency, so I can't easily replace it, even though there are pure python implementations available (not api compatible though)

- keyset sharing is very inefficient, I think an xpub based schema could work better. The mint could say "this xpub, derive keys according to standard denominations yourself". Not sure if it's interesting for cashu, maybe it could be a parameter during requesting keysets. The difference is between fitting in one packet and splitting and reassembling.

- I should pack the jsons better, in binary form and compress it.