Subject: Re: [Bitcoin-development] Payment Protocol Proposal: Invoices/Payments/Receipts

From: Mike Hearn <[email-masked]>
Date: Tue, 27 Nov 2012 13:03:35 +0100

> Further, the inclusion of x509 is not really needed in the spec - you don't need to sign the invoice with an x509, you can use the payment key.

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.