Thank you for the ideas. We will analyze them.
Nevertheless, I've from first reading some remarks:
The BTM has to be used as an entry point for bitcoins. The use of the machine is already difficult for someone who isn't aware how bitcoin wallets works. If you want on top of that use signature, only the bitcoin geek will understand. Or maybe I don't understand the point?
When buying BTC, there does not need to be a signature since the notes can be counted instantly and the BTC can be paid out.
It's for selling BTC. When you sell BTC and need to wait for confirmations, you return later to the BTM and sign a message is shows you in order to get your draghi papers.
Also, I just meant it to be an alternative so you dont have to provide your phone number. When buying, you don't need a phone number wither since you don't have to return later to collect your coins.
How do you intercept SMS? It is a very difficult task to do. The air interface between the mobile and the radio network is encrypted. As far as I know, there is no way to decrypt it on the fly.
It's not a trivial task, thats true. I honestly don't wanna talk about it in public, will send a PN.