Subject: RE: OCSP support for historical reference to certificate suspension

From: Peter Sylvester <[email-masked]>
Date: Thu, 7 Sep 2000 10:55:36 +0200 (MET DST)

> 
> > I do not see in text that something is required to do something like
> > time stamping so that a verifier has some date to use to determine
> > the validity of a cert.
> 
> the second timestamp is absolutely required to achieve non-repudiation.
> otherwise i could easily revoke my certificate at any time and claim that
> someone other signed it afterwards. no one could prove the contrary without
> a timestamp.

Unless maybe the the other party in front of you has a gun. :-) 

Time-stamp of a third party are a possible way that can help if the parties
have agreed in advance that this is the game to play, or when a law
indicates that this would be sufficient. 

Would you consider the following procedure as time stamping?
I sign something and indicate a date in it (an arbitrary one). You
are the verifier, and you give me a co-signature indicating that
you believe/agree with what I have signed.

> the first timestamp could prevent similar things. i could claim that i had
> the key-pair before i received a certificate or before it got valid. i admit
> this case is not as important as the previous one, because it is rarely
> necessary to prove that i signed something after some date. nevertheless, i
> would not ignore it.

If you consider that not being allowed to sign while a cert is suspended
and can be valid later, then this time is as important as the other one?

Instead of 'time stamps', one could also just use a OCSP responder to
validate your cert putting the message or digest or whatever as a Nonce.
Note that OCSP requests and responselist can be empty sequences,
at least in the current syntax.

---

From: "Karl Scheibelhofer" <[email-masked]>
Date: Fri, 8 Sep 2000 14:18:21 +0200

> you believe/agree with what I have signed.

if the verifier accepts your signature, it is all rigth and you two are in
business. but if your signature is legally binding (treated equally to a
handwritten signature according to law), is independent of this.

> and can be valid later, then this time is as important as the other one?

i am pleased to see that you agree.

> at least in the current syntax.

i prefer a timestamping authority to get a timestamp.

regards

  Karl