Re: Online Certificate Revocation Protocol

[jim <jimhei@xxxxxxxxxxxxxx>]

I usually try to keep a low profile, but cannot help but get involved. 
There is absolutely a need for revoking keys, even if they were destroyed. 
If I were conducting a high-risk operation (large sales, financial responsibilites,
life responsibilities in the medical community, national defense, etc.),
I would not trust any system where keys were not revoked just because someone
reported them destroyed.  The associated key could certainly be reproduced
for later usage if someone were able to figure out what was being used,
and without revocation, there would be no way to ensure that they usage
of the key did not continue after the reported destruction.  When
a key is no longer to be used other than at the end of its validity period,
it must be place on a CRL to end usage of it altogether.

I have stated it pretty strongly, but I feel that way about it.  The problem then becomes one of determining the risk mitigation with lost keys and ensuring that the mitigation is as stringent as possible to ensure less risk.  It is a matter of trust if the CP and CPS do not call for revocation and will certainly disqualify the users of such keys from access to areas where their certification is not considered suitable.  If the ability to put trust into a certificate that is then used to authenticate a user so that user can access information or workflow that they would not otherwise be able to access, then the business decision behind using that form of trust must make the risk mitigation decision to reduce the amount of trust that can be divested into a certificate from a system that does not revoke it because it is reported by the user to be destroyed.  For a system to be validated, registration and certificate issuance have to be upheld by having practices as strong for certificate revocation.  Otherwise, why have a PKI to begin with?
Jim Heimberg, ABC, Ph.D.

Santosh Chokhani wrote:

 

Destroying a private key used to generate signature may cause some operational grief in terms of getting a new key certified, but there is no need for that key any more and hence no revocation is needed.

Destroying a private decryption key also does not require any revocation, but underscores the need for key recovery.  Absent key recovery, data encrypted with the public key companion to the lost private key, can not be decrypted.

-----Original Message-----
From: Tony Bartoletti [mailto:azb@xxxxxxxx]
Sent: Friday, June 08, 2001 5:31 PM
To: Housley, Russ; pgut001@xxxxxxxxxxxxxxxxx
Cc: ietf-pkix@xxxxxxx
Subject: Re: Online Certificate Revocation Protocol

At 04:47 PM 6/8/01 -0400, Housley, Russ wrote:
>Peter:
>
>You make an interesting point.  I figure that a message signed with the
>private key that is claiming to be compromised is a good thing to pay
>attention to.
>
>If the message is from the subscriber, then that subscriber probably knows
>that some bad thing just happened and the subscriber is trying to let
>everyone know.  He does not want any one to rely on the key any more.
>
>If the message is not from the subscriber, then the key has absolutely
>been compromised.  What a nice attacker to tell everyone.
>
>Russ

Indeed.  I have often considered that a revocation request signed with the
corresponding private key is one of the few things in this world one can
act upon reliably.  If we could build whole systems on such principles,
we'd be home free.

A question:  If one discovers that they have accidently destroyed their
private key (and there is no evidence of compromise), are they under any
particular obligation to request revocation?  Is there any liability, or
other real "downside" to simply getting a new key and keeping mum about the
fate of the former key?

(I ask, because this seems the only case where a revocation request could
NOT be signed by the key in question.)

___tony___

>At 04:34 AM 6/9/2001 +0000, Peter Gutmann wrote:
>>Nada Kapidzic Cicovic <nada@xxxxxxxxxxxxx> writes:
>>
>> >This is exactly what CMP specifies. Many vendors already have support
>> for CMP
>> >EE initiated certificate revocation. The interoperability of different
>> >implementations of CMP certificate revocation (among other things) has been
>> >conducted during PKI Forum and ICSA CMP interop testing quite successfully.
>>
>>However there are two ways to look at revocation, the DOS model and the scram
>>switch model.  The DOS model says that anyone who can revoke your cert can
>>cause a DOS, so it should be made as difficult as humanly possible to
>>revoke a
>>cert.  The scram switch model says that when your private key is compromised
>>you want the cert revoked right now with no excuses, so it should be made as
>>easy as possible to revoke a cert.  CMP follows the DOS model and makes
>>it very
>>difficult (in some cases impossible) to revoke your cert.  Programs like PGP
>>follow the scram switch model (via suicide-note revocations) and make it very
>>easy to revoke your cert.  Depending on your point of view, CMP may not
>>be the
>>right thing for handling revocations.
>>
>>Peter.

Tony Bartoletti 925-422-3881 <azb@xxxxxxxx>
Information Operations, Warfare and Assurance Center
Lawrence Livermore National Laboratory
Livermore, CA 94551-9900