[OpenID] On the portability of identifiers

[Dick Hardt]

On 31-Oct-08, at 6:17 AM, Ben Laurie wrote:

> On Fri, Oct 31, 2008 at 4:17 AM, Dick Hardt <dick.hardt at gmail.com>  
> wrote:
>> I gave a presentation on this problem and a possible solution at  
>> the last
>> IIW. (I should write up a blog post or something about it.)
>> I described the problem as a loss of control of the identifier.  
>> XRIs have a
>> layer of indirection on the identifier, but there is still just the  
>> one
>> identifier, and if someone else has control of it, then they  
>> control your
>> online persona that you have established with it. Certs have a  
>> different,
>> but effectively similar problem you describe. If you lose the  
>> private key,
>> you have lost control of the identifier.
>> One way of solving this is to have more then one identifier --  
>> essentially
>> an identifier set -- so that if you lose control of one identifier,  
>> you have
>> not lost control of the identifier set. If the set has three  
>> identifiers,
>> then you only need to present two of them to show it is you, and  
>> then you
>> can substitute a new identifier so that you again have a redundant  
>> set.
>> An implementation of this would be to have two URLs and one public/ 
>> private
>> key pair. The URLs each contain a document that references the  
>> other URLs as
>> well as contains the public key. Messages are signed by the private  
>> key and
>> include a signature of the public key as well as the two URLs.  
>> Message
>> verification is done by fetching the documents at each URL and  
>> verifying the
>> signature.
>> In a world of opaque identifiers and smart clients, this all can be
>> transparent to the user. They just saw they want to log in with a  
>> particular
>> identifier set.
>> If anyone is interested in discussing this further, please let me  
>> know.
>
> I'm certainly interested in the problem, but I'm not sure this
> solution makes sense to me - certainly the concept of k of n
> identifiers being sufficient is a good one, but I'm not getting the
> details of this plan: what is the value of the signatures on the
> documents at the URLs?

Don't see where you see the signatures of the documents. The message  
is signed, not the documents.
The documents contain the public key corresponding to the private key  
used to sign the message.

The identifiers are the two URLs and the key pair.

I can write this up so that it is easier to understand if you are  
interested Ben.

-- Dick