W3C home > Mailing lists > Public > public-credentials@w3.org > March 2015

Re: Leveraging DNS and email addresses

From: Anders Rundgren <anders.rundgren.net@gmail.com>
Date: Mon, 16 Mar 2015 10:03:46 +0100
Message-ID: <55069C72.7020407@gmail.com>
To: Adrian Hope-Bailie <adrian@hopebailie.com>, W3C Credentials Community Group <public-credentials@w3.org>
The biggest confusion/mess/etc in this space is that Google consider "linkability" as a bad charecteristic which of course makes an email address the worst possible ID since it is a long-lived GUID which also tend to be exposed in various contexts.  Therefore Google's U2F presumes (according to the designers) that you have a unique identity with every provider.

Personally, I doubt that U2F will work as claimed since:
- it is awkward to have to register/signup for every site making Google and other large IdPs a logical choice for most site-owners
- you probably need a functioning email address anyway in order to have a meaningful relation with a service provider

I get a certain sense of: http://en.wikipedia.org/wiki/The_Emperor%27s_New_Clothes :-)

Anders

On 2015-03-16 09:02, Adrian Hope-Bailie wrote:
> I have been thinking lately about the challenge of keying an identity in a way that:
>
>   * Is easy to transfer and remember (even for humans)
>   * Can be normalised in a standard way and used as part of a standardised discovery process by a client to discover the Identity Provider (IdP) for that identity
>
>     /*ASIDE:* It's worth mentioning that while we strive for a fully decentralised identity system this will likely be a federated set of IdPs and for a client to traverse this web they need a starting point or primary IdP for an identity. When I talk about the IdP for an identity I am not implying there will be only 1 but that that the key/label for the identity should allow a client to resolve/discover this primary IdP and then from there discover further identity claims as required./
>
>
> To my mind the obvious solution is to use the email address format as this is already a well-known standard which user's understand.
>
> It seems to me that the only argument against an email address format is that the domain part is often not under the control of the identity owner. I don't see that is a good enough reason to force users to try and change their thinking and use URIs as their identifiers.
>
> I don't have statistics to back this up (perhaps somebody does) but I consider the relative obscurity of OpenID as a login option as evidence that this is a bad idea.
>
> So how do we help the user that has an email address @gmail.com <http://gmail.com> or @hotmail.com <http://hotmail.com> or @yahoo.com <http://yahoo.com> but wishes to host their identity themselves or at a different IdP?
>
> First, we define a mechanism or standard algorithm/protocol for translating their email address into a service discovery process that may start with their home domain but ultimately result in the client accessing the identity somewhere else. Then we pressure the large email providers to abide by this standard. I acknowledge that this may be difficult but I would say it is not impossible.
>
> I imagine the user experience being something like the following:
>
>  1. I log in to my account with this email provider, go to my account settings and prpvode the URL of my IdP.
>  2. When I use my identity online the client executes the service discovery protocol as defined, contacts my email provider and is given the URL I have configured as part of this process.
>  3. The client negotiates with my IdP of choice to get my identity information.
>
> If we have designed the protocol correctly (very close to what is already in place today) my email provider only knows who my IdP is but nothing more about the identity I have defined their unless I choose to share it.
>
> Where a user has a primary email address with a provider who is not following the standard the user has two choices:
>
>  1. Change email providers
>  2. Use an identity that is different from their primary email address.
>
>
> Option 2 can be easily facilitated by any IdP who wishes to play in this space. In conjunction with offering an IdP service they could also allow their identity key (email address) to be used as an email address by the subscriber but simply forward all emails to that address on to the primary email address of the subscriber.
>
> I think the Discovery protocol of OpenID Connect (http://openid.net/specs/openid-connect-discovery-1_0.html) is a good reference of how an email address could be used to discover the user's IdP however I'd be more in favour of leveraging the DNS service discovery protocol (RFC 6763 - http://www.dns-sd.org/).
>
> Is there a compelling case for using a URI as an identity key as opposed to the familar form of an email address?
>
> Adrian
Received on Monday, 16 March 2015 09:04:36 UTC

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