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From: Michael Gronager <gronager@ceptacle.com>
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Date: Tue, 27 Nov 2012 13:39:30 +0100
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	<CACwuEiP7CGeZZGW=mXwrFAAqbbwbrPXTPb8vOEDuO9_96hqBGg@mail.gmail.com>
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	<895A1D97-68B4-4A2F-B4A1-34814B9BA8AC@ceptacle.com>
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To: Bitcoin Dev <bitcoin-development@lists.sourceforge.net>
Subject: Re: [Bitcoin-development] Payment Protocol Proposal:
	Invoices/Payments/Receipts
Precedence: list

> No, the point of using X509 certs is to get a verified identity (a
> domain name) on the receipt, this is needed for multi-factor
> authentication. You can't do that without some kind of third party
> asserting to an identity.


Agree that you need a third party to verify identity. But the =
verification policy of sites is the job for a payment provider not a =
payment technology. So if you would like verification of the site you =
could just sign the memo using standard S/MIME - why mix it with the =
payment protocol?

Further, it is controversial use of the host key to use it for digital =
signing of documents, and not even within the policy of a host =
certificate as far as I recall.

The problem you are trying to tackle is that we don't have an ID =
solution on the internet today for this purpose. Certificates for =
signing messages are distributed freely and insecurely only based on =
temporarily having an email from within an organization, and the host =
certificates are meant for SSL handshakes. Funnily, any CA can issue =
digital certificates for email signing for any domain, even though they =
don't own them, and without notifying the owner. DANE actually solves =
this, but until then using the host certificates is unintended use, it =
is cryptographically a nice solution, but legally and standard-wise a =
hack.

/M=