Subject: Re: PKI International Consortium

From: [email-masked]
Date: Sun, 4 Apr 2004 13:02:47 MET

Hi,

> If a relying party needs to know that I possess certain attributes, and
> if I can present an "Attribute Certificate" that convinces them that I
> do indeed possess those attributes, then what purpose is served by also
> having me present an "Identity Certificate"?

You are completely right, Eric. There are many situations that require
the knowledge of certain attributes but do not require knowledge of identity.
For instance, accesing the Playboy should require knowledge of the user being 
over 18, but no identity information should be revealed. The paragraph about 
X.509 was extracted from a paper on interoperable access control for digital 
libraries [1]. In that paper we defend the idea of using no identity, or at 
least making the authorization usable without identity. This paragraph is also 
extracted from [1]:

"Most of current access control schemes base their authorization approaches on 
locally-issued credentials that are linked to user identities. This type of 
credentials present many drawbacks. Among them we highlight: (a) they are not 
interoperable; (b) credentials for the same attribute are issued many times 
for each user, what introduces management and inconsistency problems; (c) 
credentials are issued by the Digital Library administrator, however, in most 
cases, the administrator does not have enough information or resources to 
establish trustworthy credentials; and (d) they are dependent on user 
identity. In practice, it is frequent that the identity of the user is not 
relevant for the access decision. Sometimes it is even desirable that the 
identity is not considered or revealed. Furthermore, in systems based on 
identity, the lack of a global authentication infrastructure (a global Public 
Key Infrastructure, PKI) forces the use of local authentication schemes. "

So, again, in the design of Identity Certificates we should concentrate on 
Identity issues, and on the needs of systems requiring identification. Trying 
to use Identity Certificates for other uses is wrong.

Antonio Maña.

-------
[1] Yagüe, M.I., Maña, A., López, J., Pimentel, E., Troya, J.M. A Secure 
Solution for Commercial Digital Libraries. Online Information Review Journal, 
Vol. 27 Issue 3, pp. 147-159, Emerald, June 2003.

> > There are, however, reasons to have more than one identity certificate, but
> > these are related to privacy, anonymity and sometimes legal reasons.
> 
> And I'm considering the possibility that there might be reasons to have
> fewer than one identity certificate.
> 
> 
> Eric Norman
> 
> 	"Congress shall make no law restricting the size of integers
> 	that may be multiplied together, or the number of times that
> 	an integer may be multiplied by itself, or the modulus by
> 	which an integer may be reduced".
> 
> 

------------------------------------------------------
Mensaje enviado desde el Servidor de Correo del
Departamento de Lenguajes y Ciencias de la Computacion
de la Universidad de Malaga
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From: Eric Norman <[email-masked]>
Date: Sun, 4 Apr 2004 19:50:34 -0500 (CDT)

> to use Identity Certificates for other uses is wrong.

Well, my opinion is that you won't have much luck dealing with "Identity
issues" until you have a good definition of "identity".

Here's my shot at it.  If you start from the premise that identity is
just a set of attributes, then your identity is those attributes that
are constant and last forever.

So, my "Identity certificate" asserts an association between me and
the University of Wisconsin.  Is that part of my identity?  It depends
on how you interpret that assertion.  If you interpret it as "was at
one time affiliated with that university", then that lasts forever and
it is (Winston Smith to the contrary).  If you interpret it as "is
currently affiliated...", then it isn't.

The only observation I can make right now is that with the former
interpretation, Lynn Wheeler doesn't get to use the adjectives "stale"
and "static".  Whether that's any more useful than counting angels
dancing on pinheads remains to be seen, I suppose.

Eric Norman

---

From: "Al Arsenault" <[email-masked]>
Date: Sun, 4 Apr 2004 21:19:23 -0400

> are constant and last forever.

AWA:  "reasonably forever". :-) There aren't any attributes guaranteed to last forever.  People change their names, for reasons of marriage, divorce, or because they just want to.  Affiliations - employers, university attended, etc. - change when circumstances change. 

> dancing on pinheads remains to be seen, I suppose.

AWA:  I tend to agree with this.
 
> 	which an integer may be reduced".

		Al Arsenault
		BBN Technologies 

	(should I add "no longer a Verizon company"?  :-)

---

From: Ed Gerck <[email-masked]>
Date: Sun, 04 Apr 2004 20:13:22 -0700

> are constant and last forever.

Not even your fingerprints are constant and last forever (or, for your 
lifetime).

Identity is not a thing or a set of things. Identity is the connection
-- to identify is to seek connections [1]. In identification we look for 
logical or natural connections, where absence of connections also counts. 
For example:

- between a fingerprint and the person that has it,
- between a PK certificate and its private key,
- between a name and the person that answers by that name,
- between an Internet host and a URL that connects to it,
- between an idea and the way we can represent it in words,
- conversely, between words and the ideas they represent,
- etc.

Identification can thus be understood not only in the sense of an
"identity" connection, but in the wider sense of any connection.

That's why it does not make much sense to have *one* identity certificate
-- we do have many identities (connections) and we may need to use them 
in separate. Which one to use is just a matter of protocol expression, 
need, cost and (very importantly) privacy concerns [1]. 

Cheers,
Ed Gerck

[1] For my '98 draft on this concept, please see 
http://nma.com/mcg-mirror/coherence.txt
This work shows that not identity but coherence (as natural or logical
connections) is the general metric for identification. More coherence 
and more coherence modes mean stronger identification, even if anonymous.

---

From: "Al Arsenault" <[email-masked]>
Date: Sun, 4 Apr 2004 21:19:23 -0400

Al Arsenault
		BBN Technologies

---

From: "todd glassey" <[email-masked]>
Date: Thu, 8 Apr 2004 19:02:08 -0700

----- Original Message ----- 
From: "Al Arsenault" <[email-masked]>
To: "Eric Norman" <[email-masked]>; "PKIX list" <[email-masked]>
Sent: Sunday, April 04, 2004 6:19 PM
Subject: RE: Identity (was PKI International Consortium)

> AWA:  "reasonably forever". :-) There aren't any attributes guaranteed to
last forever.  People change their names, for reasons of marriage, divorce,
or because they just want to.  Affiliations - employers, university
attended, etc. - change when circumstances change.

DNA is reasonably constant