On 02/06/2015 12:59 AM, Roy Badami wrote:
>> In this case there is no need for P2P communication, just pay to an
>> address you already have for the other party. If you want to avoid
>> address reuse, use stealth addressing.
>>
>> But yes, if you don't have a stealth address for the other party you can
>> certainly communicate in private as peers where you trust that you share
>> a public key. The core issue here is really bootstrapping of that trust
>> in an ad hoc manner.
> 
> Something interactive might still be nicer, though, to avoid the risk
> of paying to an address that the payee no longer has the private key
> for.  "Nooo!! Don't pay to that address.  I lost my old phone so I
> generated a new wallet."

Certainly, which brings us back to proximity.

Which reminds me - it's important to keep in mind the scenario that
arises when there is no person present to represent the receiver. Such
as a vending machine purchase.

Proximity in these cases is insufficient, as the receiver is not able to
prevent application of a fraudulent NFC device or replacement of a
static QR code. In these cases BIP-70 becomes essential.

e