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Re:Who cares what MUST be signed? (was Locations...)

From: Andreas Schmidt <aschmidt@darmstadt.gmd.de>
Date: Thu, 02 Dec 1999 12:16:58 +0100
Message-ID: <3846552A.B627DB92@darmstadt.gmd.de>
To: Daniel LaLiberte <liberte@w3.org>, Mark Bartel <mbartel@thistle.ca>
CC: XMLDSig WG mailing list <w3c-ietf-xmldsig@w3.org>
Daniel LaLiberte writes:

>To reiterate, it seems that it is ONLY the verifier that cares what is
>signed.  When does the signer really WANT to sign something except to
>satisfy the needs of verifiers.  What advanatage does the signer have?
>A signature seems to only obligate the signer.

Regarding this general point, I have have a quite different view. I see
signatures as part of messages addressed to a certain recipient. Thus
they are special assertions that the signer wants to transmit (that is,
I think of signed documents as speech acts). I think the view that
signatures meaning and content are determined by the verifier stems from
the fact that, in most cases, there is a _final_ recipient (a court) who
takes the special role to prove or disprove the assertions made by the
signer - and often the signature will be practically designed after the
requirements of that verifier.
  I think there are many examples where the primary addressee of a
signed message is not even a priori determined - it may even be the
whole public as in copyright statements like digital watermarks. Even in
the case of a check, the assertive message character is quite clear
("Pay on behalf of [signer] ...") - and You don't have to use the banks
check form to make such a statement legally binding.
  Nevertheless, I do not see which restrictions the verifyer-oriented
view would pose on any syntax with which one wants to express
general-purpose digital signatures. Could You state for example, what
kind of assertions and syntax would be ruled out by Your view (e.g.
unsigned locations) and why? In fact, I would oppose any requirement You
would draw from Your viewpoint, that restricts the signers expressivity
beyond the syntactic restrictions posed by the current draft.

>Daniel LaLiberte

Dr. Andreas U. Schmidt, Dept. SIT | mailto:aschmidt@darmstadt.gmd.de
GMD German National Research      | phone :+49-6151-869-712       
Center for Information Technology | fax   :+49-6151-869-704
Received on Thursday, 2 December 1999 06:16:01 UTC

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