Subject: Re: OCSP and German Law

From: Stefan Kelm <[email-masked]>
Date: Fri, 25 Feb 2000 10:40:29 +0100 (MET)

Johan,

> I agree to Stefan, I bet a box of beer that the "validity model" in the
> German Law won't change.

According to the (still internal) drafts of the new law it won't change at all.

> The advantage is more or less of legal and/or organizational nature. If the
> CA signs a certificate, the PSE (e.g. your smart card with your *private*
> key) has to be delivered in a secure way to the owner.
>
> In technical terms the certificate is almost valid (but not in legal terms).
> But the PSE hasn't handed out to the owner yet, - with all possibilities of
> abuse (I know there are ways to handle it in another way). But if you wait
> until the owner proofs that he received the PSE, to say the certificate is
> valid you avoid this insecure time gap. The validation is manifested by
> publishing the certificate.
>
> So I hope you see the rational of this validity model.

I think this is pretty plausible. However, using this model the directory
is much more burdened with security issues than usual. Denial-of-service
attacks against the directory become much more crucial, IMHO. If someone
doesn't want your certificate to be validated (e.g., because you digitally
signed an order to buy one million new shares of that interesting company
and the attacker doesn't like that) he shuts down the directory server
for a while.

Cheers,

        Stefan.

______________________________________________________________________________
Stefan Kelm            PGP key: "finger [email-masked]" or via key server
DFN-PCA                                                      <[email-masked]>
Vogt-Koelln-Str. 30                               http://www.pca.dfn.de/~kelm/
22527 Hamburg (Germany)                   Tel: +49 40 428 83-2262 / Fax: -2241

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From: Michael Herfert <[email-masked]>
Date: Fri, 25 Feb 2000 16:09:04 +0100

Hallo,

Stefan Kelm wrote:
> If someone

Consider the X.509 standard model:
If the verifier receives a high value transaction 
he asks his standard OCSP service in order to 
be sure that the certificate ist not revoked.
This standard service may be attacked in the same
was as in the SigG case.
So there is no difference with respect to this attack.

Michael 

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Michael Herfert
GMD - German National Research Center for Information Technology
Darmstadt
Germany