On Wed, 16 Nov 2005, silverhairbp wrote:
Lets review this.
OK
If a new certificate is issued with different information but the same public
key and serial number as the original, then there is no point in reissuing
since the original certificate can't be CRL'ed and will still be active
through its life. That is one of the reasons why each certificate MUST have
a unique serial number.
I think the point of discussion is 'new certificate' here. It is the same
certificate as before. Only the encoding is different, but their
signatures are identical, and therefore trust validation yields the same
with either copies. They have the same Subject/Issuer DN. The same public
key. The same extensions (well, almost, that is). The same fingerprints.
The same validity period. They provide exactly the same level of trust for
the relying parties. It is not a 'new certificate' by any stretch of the
imagination.
And, of course, the original "can't be CRL'ed," I said the exact same
thing. There is no point in revoking a self-signed certificate, if your CA
signing keypair has to be changed. In any case of key changeover, you roll
out a new PKI, and destroy the old keypair. You must have a working, safe
root cert distribution mechanism to the relying parties anyway.
It is NEVER permissible to reissue a certificate reusing a serial number.
Well, first of all this is generally very true - this is a special case,
however. Secondly, it is not quite 'reissued,' see above.
Each certificate must have a unique serial number.
Yes. Same certificate -> same serial.
The scheme descrived by David REQUIRES the extablishment of a new certificate
hierarchy with a new root certificate.
Well, I don't quite agree. If the level of trust put in signatures does
not change with this technical alteration, I see no reason for a key
changeover. It is only a different version of the same root cert with
notably one single different value for an extension.
It is only bad practice to reuse a key pair.
Again, generally this is very true. But this is not an actual re-use.
Szabolcs
Bill
Hernath Szabolcs wrote:
On Wed, 16 Nov 2005, David Bannon wrote:
OK Hernath, that makes sense. But how do I get OpenCA to accept a new,
additional certificate if it does not make it itself ? I tricked it
How do you mean accept?
into letting me make a new one (by removing the existing files) but if I
Sorry, I don't get it...
generate a new certificate externally and then just put the files where
OpenCA keeps them, OpenCA will not notice and won't add them to its
I don't have access to my signing machine right now, but I think you
should simply overwrite all instances of the CA root cert within opencas
directory tree with the new version.
Szabolcs
database.
David
PS : When this is all over, I'll write up the procedure for the FAQ,
other people must want this occasionally !
On Wed, 2005-11-16 at 11:40 +0100, Hernath Szabolcs wrote:
Hi,
On Wed, 16 Nov 2005, David Bannon wrote:
Is it necessary for the start and end dates to be the same as the
original ? Means I cannot use the OpenCA gui to create it but thats
not
too much of a problem.
You certainly don't want to change the start of validity date of your
root
certificate, so you have to create it by hand. You may change the end
date
if necessary. In any way, the change (even if you only alter the
keyUsage
criticality) should be reflected in your new CP/CPS version.
Szabolcs
Would make life a lot easier !
David
Hi All,
On Tue, 15 Nov 2005, silverhairbp wrote:
David Bannon wrote:
Folks, I would like to ask for some advice here. We have a
problem and
below is our plan to solve it. I'd be very grateful if you
could have a
look at it and let me know if you see anything thats going to
bite us
expectantly.
The problem
-----------
We use OpenCA 0.9.2 and it was setup some 12 months ago using
default
settings. Our CA Certificate was originally issued without the
necessary
parameter of keyUsage being 'critical'.
The solution
------------
Revoke all 220 certificates, revoke the CA Certificate, issue
a new CA
certificate (using existing key) and issue new certificates to
users.
I think you should not do that. If the only thing you want to
change is
technical parameters in your root cert, but otherwise use the same
keypair, you essentially maintain the trust based on the the
signatures
made with your original signing key. In other words, you do not
need to
revoke anything, instead you simply reissue your root cert with
the same
DN, serial, keypair and validity dates and changed technical
parameters
(e.g., fixing the keyUsage, changing the signature algorithm etc).
In this
way, signatures made with the old or new root certs will validate
against
either of them. The already issued certificates will not be
effected.
Besides, there is no point in revoking a self-signed certificate
anyway,
in case you want to terminate the trust associated with the
signatures
made with a CA's signing key before the expiration of the root
cert
(emergency key changeover), you revoke all issued certificates
(except the
root), publish a last valid CRL, destroy all copies of the CA
signing key,
and start anew with a fresh PKI.
If you only want to terminate the usage of a CA's signing key
-without
disruption of the trust associated with its signatures- (routine
key
changeover), you can harmonize various validity dates and CRL
issuance
frequency such that you can keep your usual operating procedures
(issuing
CRLs as usual) and let all certs (issued and root) expire. Before
that
happens, you already start your fresh PKI in parrallel with some
useful
overlap time.
Good Luck,
Cheers
Szabolcs
P.S.: as a sidenote, if the keypair of sub-CA is actually
compromised in a
multilevel hierarchy (as opposed to having some flags
misconfigured), I
would definitely *revoke* the sub-CA's root certificate for good,
not only
suspend it. The keypair is the root of your trust - if it's
compromised,
your pki (under that sub-CA's level) is over.
The Plan
------------
We have established that we can generate a new CA Certificate
and OpenCA
(0.9.2) is quite happy. So this is what we'll do, steps 1 - 3
(below)
must be done before implementation date.
1) Encourage all end users and RA Operators to lodge new
requests for
new certificates.
2) Ordinary users must meet (again) with RA Operators to show
photo ID.
RAO must authorise new applications in normal manner.
3) CA Operators and CA Manager will phone RAOs to explicitly
confirm
details of their own personal applications, in normal manner.
------ Implementation Day --------
4) On the CA machine, move the existing CA Certificate files
(from /var/crypto/cacerts) out of the way. Their details will
remain in
the database. Start openCA, make a new request for a self
signed
certificate and then Generate it.
(General->Initialization->Request
Setup, Certificate Setup).
5) On RA, revoke all user certificates and process to CA.
6) On RA, revoke the old CA Certificate and process to CA.
7) Commence issuing the backlog of certificate requests
currently
pending, in the normal manner.
Although we will aim for completing this process in one day, I
doubt we
will be able to do so.
--------------------
I'll be very grateful for any comments you care to make.
David
Rather than revoking the original CA certificate, have you
considerd
suspending it to see if there are any user that have not
installed their new
certificates? It would be easy to roll back the old root cert
and convert
that last users, repead the suspend root process until all users
are
converted. That way you can motivate slow converters to get new
certificates
while minimizing their down time.
As a suggestion, when deploying the new hierarchy, manage the
validity period
closely so taht you can migrate to a new root without a lot of
hassle. There
are papers on the technique available.
Bill
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