On 19-Jan-06, at 2:02 PM, Ben Laurie wrote:
Dick Hardt wrote:
On 19-Jan-06, at 5:27 AM, Ben Laurie wrote:
John Merrells wrote:
An identity information exchange should involve just three
parties: the
user, their agent, and a relying party. The user’s agent is
where they
authenticate themselves and a repository where they store their
identity
information, and the relying party is an entity requesting identity
information.
This seems overly prescriptive. In particular, it would appear to
exclude any kind of temporary certificate. It also excludes
proxies. Oh,
and the case where authentication occurs elsewhere.
Hey Ben, would you take the time to write up simple use cases for
your
three points so that we (or at least I) can understand them?
Temporary certificate
This is to satisfy the minimality requirement. User has cert including
date of birth, say, and wants to prove he's over 21. So, he (or his
agent) shows the cert to some CA that produces a temporary cert for
him
saying he's over 21, which he or his agent then shows to the
relying party.
Note that this only half gets you unlinkability if the certs are
anything conventional because the CA can link the permanent and
temporary certs.
The CA is, of course, a fourth party in the transaction.
I understand this one.
Proxy
Not sure exactly what to say about this, except that a proxy could sit
between any of these parties, and the language above assumes that
it can
do so both transparently and securely. Which may not be so (that
is, it
may have to be non-transparent to remain secure) if it adds
functionality, like caching, or anonymising.
I understand what you are saying here as well (proxy has a number of
meanings)
Authentication Elsewhere
It may turn out that for whatever reason I have to use multiple
agents,
so I'd like to authenticate them via my meta-agent. Unlinkably.
I would say that the meta-agent is your agent.
I think that John's identity exchange description above needs fleshed
out some more.
The obvious missing party that *may* be in the transaction is a 3rd
party making a claim about the user, that is part of the transaction
when viewed holistically.
-- Dick
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