Dear Mr. Lowry:
You and mr. G. Bailey have raised some very significant
questions, related not only to our current PEM implementation,
but I should say to the whole PEM specifications.
1. Our CURRENT PEM implementation does not distribute CRLs,
but one of the future versions will. Our current approach
is based on availability (by users) of CURRENTLY VALID
certificates, vs. all revoked certificates. After all,
those are that you need.
2. I wonder, if you don't trust some CA to send you CURRENTLY
VALID certificates in the path of your partner, how can
you trust the same CA to send you the CRL, when both
messages are THE SAME TYPE of the PEM letter (MIC-ONLY).
3. The problem of stolen certificates (challenged to our
implementation !) is in fact the problem of the "delay"
period. But that period exists even in current PEM RFCs,
since CRLs are distributed only periodically. I wonder
how mr. Bailey would solve his problem of stolen
certificate in the period while victim's partners still
haven't received the CRL.
4. The problem of criminal family, i.e. false CA: In our
implementation, in order to keep strict hierarchy of
CAs, that is not possible, since our every CA "knows"
its upper level CA and its subordinate level CAs.
If CA structure is "open system", so that any entity
being able to perform CA functions can apply and be
registered by any other CA, how the hierarchy can be
guaranteed.
5. Regardless of our "acceptance" of the necessity of CRLs,
I must admit that I don't see even in the coming versions
of our system how they will be implemented, since, as much
as I understand PEM RFCs, EVERY USER MUST HAVE ALL THE CRLs
of ALL CAs above ALL OF HIS PARTNERS !!! Next, when some
user sends a new certificate to CA, i.e. declares the current
as revoked, how that CA will know where (around the world)
that user has distributed his certificate and where to send
the CRL.
I would like to emphasize again that IN THIS STAGE and IN THIS
VERSION of COST-PEM system, we didn't pay so much attention
to the CRLs, what I have explicitely stated in our PCA
policy. Therefore, I do not claim that our system is fully
in compliance with PEM RFCs, but I am sure that it is
WORKABLE and represents a good basis for initial practical
experience of our (future) users and a good basis for
further improvements.
Regards,
Sead Muftic
COST Computer Security Technologies AB
Stockholm, Sweden