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Date: Fri, 6 Feb 2015 00:36:11 +0100
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From: =?UTF-8?B?TeKStnJ0aW4gSOKStmJv4pOLxaF0aWFr?=
	<martin.habovstiak@gmail.com>
To: Eric Voskuil <eric@voskuil.org>
Content-Type: text/plain; charset=UTF-8
Cc: Bitcoin Dev <bitcoin-development@lists.sourceforge.net>,
	Paul Puey <paul@airbitz.co>
Subject: Re: [Bitcoin-development] Proposal for P2P Wireless (Bluetooth LE)
 transfer of Payment URI
Precedence: list

> A BIP-70 signed payment request in the initial broadcast can resolve the
> integrity issues, but because of the public nature of the broadcast
> coupled with strong public identity, the privacy compromise is much
> worse. Now transactions are cryptographically tainted.
>
> This is also the problem with BIP-70 over the web. TLS and other
> security precautions aside, an interloper on the communication, desktop,
> datacenter, etc., can capture payment requests and strongly correlate
> transactions to identities in an automated manner. The payment request
> must be kept private between the parties, and that's hard to do.

What about using encryption with forward secrecy? Merchant would
generate signed request containing public ECDH part, buyer would send
back transaction encrypted with ECDH and his public ECDH part. If
receiving address/amount is meant to be private, use commit protocol
(see ZRTP/RedPhone) and short authentication phrase (which is hard to
spoof thanks to commit protocol - see RedPhone)?