Re: What are certificates fundamentally all about? [was: draft-turner-caclearanceconstraints-01.txt]

[Stephen Kent <[e-mail]>]

At 8:40 AM -0500 10/13/08, Timothy J. Miller wrote:
>Stephen Wilson wrote:
>
>>Then you can subtly adjust the conception of a PKC as being "an 
>>assertion of an entity's key and a RELATIVELY STATIC identity IN A 
>>DEFINED CONTEXT".  A flexible interpretation of "identity in a 
>>defined context" embraces things like my identity as an chartered 
>>engineer, my identity as a business owner, my identity as a health 
>>insurance subscriber, my identity as a bank account holder.  In 
>>each of these scenarios, it would be very powerful for me to carry 
>>a separate dedicated certificate with which to sign specific types 
>>of transactions (e.g. engineering test reports, tax returns, health 
>>insurance claims, and payment instructions respectively).  That is, 
>>four different certificates all independently registered and 
>>managed, tightly coupled to regular customer relationship 
>>management processes, probably carried on separate smartcards.
>
>We have that; it's called SPKI/SDSI.  :)

No, it's called not VeriSign :-).

I authored a paper in 1997 that made the same argument as Stephen 
Wilson did (maybe it's a Stephen thing). Moreover, there is a report 
published in 2003 by the National Academies Press ("Who Goes There? 
Authentication Through the Lens of Privacy?") that also observes that 
an individual does not have just one identity, and thus we ought not 
assume that a single cert will suffice to identify/authorize an 
individual.


Moreover, arguments that clearances are not sufficiently long-lived 
to be put into certs do not match lots of experience.  Basic 
clearance info (vs. compartments) tends to be very stable, for 
multiple years, in the the U.S. DoD.  They have issued certs 
containing clearance info for a while, and not found that clearance 
changes create undue CRL activity. They have issued certs with more 
than just basic clearance info, e.g., to secure phones and data 
encryption devices, and those too have proved to be long-lived. So we 
ought not waste time debating this aspect of the proposal, because 
there is enough experience to resolve these specific arguments.

Steve