Subject: Re: [Bitcoin-development] Payment Protocol for Face-to-face Payments

From: Mike Hearn <[email-masked]>
Date: Thu, 27 Mar 2014 11:08:22 +0100

>
> But these cases are the norm, rather than the exception.
>

Well, you're lucky, you live in Berlin. Most of the payments I make with
Bitcoin are online, to websites. So this will differ between people.

I wonder how critical it is. Let's say you are paying for a meal. In your
head the place you're at is just "the little Indian restaurant on the
corner". In the companies register and therefore certificate it's something
like "Singh Food GmbH". That's probably good enough to prevent shenanigans.
Even if there's a virus on your phone, it can't really replace the cert
with a random stolen one, otherwise your meal could show up like "IronCore
Steel Inc" or something that's obviously bogus. It'd have to be an
incredibly smart virus that knew how to substitute one name for a different
one, from a large library of stolen identities, such that the swap seemed
plausible. That sounds very hard, certainly too hard to bother with for
stealing restaurant fees.

And if a waiter at the restaurant is corrupt and they replace the cert with
one that's for their own 1-man business "BP-Gupta" or something, OK, you
might pay the wrong person by mistake. But eventually the corrupt waiter
will be discovered and then someone will have proof of what they did. It's
FAR more likely they'd just strip the signature entirely and try to
convince you the restaurant doesn't use BIP70 at all.

Still, if we want to fix this, one approach I was thinking about is to have
a super-cheesy CA just for us that issues certs with addresses in them, for
any name you ask for. That is, if you say you want a cert for "Shamrock
Irish Pub, Wollishofen, Zurich, CH" then it either sends a postcard to that
address with a code to check ownership of the address, or it checks
ownership of the place on Google Maps (which does the same postcard trick
but for free!).

That doesn't work for vending machines, but perhaps we just don't care
about those. If a MITM steals your lunch money, boo hoo.