Quote from: gentlemand on July 30, 2016, 10:14:32 PM

Yes. Our German teacher told us some UK coin, can't remember what it was, was accepted as a Deutschmark in German vending machines which saved my little friends rather a lot of money on school trips.

I knew a guy whose full time living was going around vending machines with an official-looking vest and a nefariously obtained copy of a key and emptying them. It looked like extremely lucrative 'work'.

Probably was. Those things accept up to 2.5k each transaction if I remember correctly. It could do it for multiple people, too.

Quote from: franky1 on July 30, 2016, 10:15:54 PM

Quote from: biggus dickus on July 30, 2016, 10:06:11 PM

I doubt accepting unconfirmed Bitcoin transactions as payment would cost a machine operator much in double spends. It's too much work to attempt a double spend for a bar of chocolate.

double spends are actually easier then you think.
small items are treated as dust. so send a payment with zero fee to the vending machine. and also on a phone send the same inputs to yourself with a fee.. 98% of the time the tx with fee going back to you gets accepted. and the zero fee drops off the mempool unconfirmed.

all it takes is 2 transactions.

to make it easier. if you know the PUSHTX addresses of pools, to API call your tx (with fee to yourself) to the pool direct, and know the ip addresses of the vending machines block explorer to send the zero fee tx. you can time it right to send the zero fee tx to the vending machine. and get ur food and send the other tx (to yourself) to the mining pool to get the better chance of both "businesses"/nodes not seeing the other tx first

it doesnt require any expensive equipment. just good timing

I think that what he's trying to say is that no-one will be bothered to. But in actuality, you could even make a script for double-spending.

Quote from: Snorek on July 30, 2016, 10:25:05 PM

Quote from: gentlemand on July 30, 2016, 09:37:02 PM

I'm more concerned about someone inventing a vending machine that doesn't use those piece of shit curly things to spit your stuff out. I've been denied my refreshment three times in a row when they jammed. Clearly they have failed to address this problem.

Haha. Touching story, but that is beside the point. The main idea is to create working and simple Bitcoin powered vending machine.
That spiral feeder you talk about is industry standard in machines like this. Smart heads need to design easy system to prevent double spending first.

Lightning... Network?