Re: German Law and OCSP

[Michael Herfert <michael.herfert@xxxxxx>]

Hello,

Hans Nilsson wrote:
> (For non-German speakers: "Good" means that the certificate is issued by the
> CA, known in the Directory and not revoked)
> 
> This is quite a different interpretation of "good" from RFC 2560, where
> "good" not necessarily means that the certificate has been issued!!!

there are two important differences between standard OCSP and SigG OCSP:

1. The meaning of "good":
   I think Hans is right in this point.

2. The single request extension certHash:
   The german law requires that user certificates must 
   be valid, even if the CA key has been corrupted.
   The extensions certHash contains the hash value of the certificate 
   being asked. It is a MUST in every request. 
   Without this value the service would not work 
   according to the law because the identification of a certificate by 
   (issuerNameHash, issuerKeyHash, serialNumber)
   is only a valid reference if the CA cert signing key is okay.
   Assume Alice has the serial number 5.
   In a desaster case where the CA cert signing key has been broken,
   an attacker may generate a certificate for Bob which has the 
   serial number 5, too. 
   In the same matter he may generate many faked certificates 
   that share a serial number with a correct certificate.
   

Michael 

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