Re: PKIX Roadmap

[Stefan Santesson <stefan@xxxxxxxxxxx>]

Al,

I finally got time to look a little bit deeper into the roadmap document.
I think it is very well formed but I have some minor disagreements.

1) Concerning definition and use of the term Root CA
2) Result from CA compromise
3) Use of certificates.

1 - Root CA
---------
Definition and use of the term Root CA in sections 2, 3.4.5 and 5.1.2 gives
the impression that Root CA is at the top of some hierarchy. 

This does not seem to harmonize with the definition of root CA in
"Certificate Management Protocols"

  "We use the term "root CA" to indicate a CA that is directly trusted by 
   an end entity; that is, securely acquiring the value of a root CA public 
   key requires some out-of-band step(s). This term is not meant to imply 
   that a root CA is necessarily at the top of any hierarchy, simply that 
   the CA in question is trusted directly."

So in fact every CA in a domain is likely to be "root" for some of its
subscribers.
I personally prefer the rem "Top CA" when describing a hierarchy.


2 - CA compromise
------------------
In section 3.4.5 it is said that compromise of a root CA is always
catastrophic and that the entire infrastructure subordinate to that root CA
has to be dismantled and started over again. This gives the impression that
a subordinate CA has to be dismatled.

My comment is that 
a) Since the rootCA does not denote any hierarchy we can't define which CA
that is subordinate or not to a specific root CA
b) A compromised CA does only require that particular CA to be dismantled.
No other non-compromised CA has to be dismantled. Other CA:s has to revoke
cross certificates to th compromised CA and all subscribers using the
compromised CA as root CA, are totally cut off until they get another
rootCA key, but that's another aspect.

3 - Certificate usage
---------------------
Section 3.1 states that:
"Certificates is used in the process of validating signed data."
This definition is leaving out any use for the purpose of encryption. I.e.
data encryption, key agreement and key exchange.


Regards
/Stefan
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Stefan Santesson                <stefan@accurata.se>
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