Subject: CyberPhone Trust Propagation Was: A $25,000,000,000 PKI

From: "Anders Rundgren" <[email-masked]>
Date: Fri, 9 Apr 1999 07:15:58 +0100

Steve,

Sorry for changing subject all the time but there are soo many issues
to discuss.  This is an explantation on a major issue regarding private keys and
trust.  Don't be fooled by the language or terminology that may suck a bit
since neither English or this part of PKI is a speciality of mine.  I am sort of
a hands-on guy rather than a philosopher.

Basically I feel that you and many others believe that CyberPhone with its
intermediary key-server, propagates trust from the client to the end-RP.

This is definitely possible and true if CyberPhone is used in the same context as
Kerberos.  I.e. for authentication and authorization WITHIN an organization
(putting on my marketing hat I would say CyberPhone does this much better
than Kerberos as the former is 100% based on PKI).

Now to the scenarios presented on my web (Shared Certificates
and Dynamic Certificates) that represent two much more complicated situations
that an open environment introduce.

If those scenarious introduce trust propagation it would mean that the intermediary
private key server performed something on behalf of the client.  But, IT IS THE
OTHER WAY AROUND!  It is the intermediary server that grants a client the right
to perform a purchase on the servers behalf.  Yes, when you purchase for a company
it is the company that buys.  That the purchase was initiated by the client does
not change this a single bit.  A company assumes that you do your work  - not that it has
to screem and shout to make you perform!  And you have in this role obligations
only to your company (=server).

That is why CyberPhone does not break any (of the mostly unwritten) rules regarding
key use and trust.

It does though assume that a server and private keys stored on it can be responsible
in the same way as a natural person.  As I wrote in another posting this is what is
happening all the time (except for signatures that are not yet implemented) in automated
invoicing systems so there is "Nothing new under the Sun".  

Regards
Anders

http://www.mobilephones-tng.com

<snip>

>>So what is so fundamentally flawed in the CyberPhone concept with respect
>>to digital
>>signature laws?
>
>I won't comment on the question of the legality of CyberPhone, vis a vis,
>the current hodge podge of digital signature laws.  However, I was not
>aware of SET wallte servers, e.g., in the corporate context you describe.
>An employee using a cert issued for company purchasing, etc. may or may not
>be the real "owner" of the private key.  If the cert identifies the subject
>as a role, and the user is the role occupant, then the company is
>intentionally maintaining accountability on a purely internal basis.
>Technicall, this can be done reasonably well by issuing the cert via a
>smart card or PC card, so that the user has not (easy) access or knowledge
>of the private key.  However, if the subject of the cert is an
>organizationl person (not role), then I think of the issue of ownership
>differently.  The company needs to revoke the cert when the employee leaves
>of changes roles and no longer has the same purchasing authoirzation.  (Of
>course, this points out why an attribute cert might be better in this case
>...)
>
>steve
>

---

From: Stephen Kent <[email-masked]>
Date: Fri, 9 Apr 1999 16:24:15 -0400

Anders,

<snip>

>only to your company (=server).

It is not the server that grants the user the right to purchase, it is the
company.  The company can choose to do this in various ways, as described
in earlier messages.  Your approach introduces added vulnerabilities into
the system, realtive to a model in which the purchasing agent directly
controls his/her private key.

>invoicing systems so there is "Nothing new under the Sun".

Servers are not principles (a security term of art), i.e., they are not
accountable entities.  Only people are. Putting a collection of private
keys on a server creates a new opportunity for someone other than the
accountable entity (user) to cause objects to be signed on behalf of the
user.  yes, many automated systems in the current environemnt offer poor
security, such as the one you describe.  I hate to see the veneer of PKI
applied to a system that retains the many of the security problems of these
existing systems.

Steve