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Re: Signing and Verifying RDF Datasets for Dummies (like Me!)

From: Peter Patel-Schneider <pfpschneider@gmail.com>
Date: Mon, 14 Jun 2021 19:43:32 -0400
Message-ID: <72c0a015527e50146dda19b84bf0b3c965fa7b6b.camel@gmail.com>
To: Eric Prud'hommeaux <eric@w3.org>
Cc: semantic-web@w3.org
On Mon, 2021-06-14 at 23:57 +0200, Eric Prud'hommeaux wrote:
> On Sun, Jun 13, 2021 at 04:26:57PM -0400, Peter F. Patel-Schneider
> wrote:
> > 
> > On 6/13/21 10:45 AM, Eric Prud'hommeaux wrote:
> > > On Sun, Jun 13, 2021 at 08:55:34AM -0400, Peter F.
[...]
> > > 
> > > If you're OK with appending a signature to a document, how about
> > > appending a signature to an N-Quads representation of a graph?
> > Oh, yes, this is fine.   N-Quads has a unique expansion to triples.
> > (Module
> > case normalization of language tags.)
> 
> Crap, I missed a step here. I wanted to explicitly ask about adding a
> signature to the RDF graph (à la the examples in
> <   
> https://janeirodigital.github.io/rdf-sig-playground/index?manifestURL=examples/toy.yaml
> >
> ). I think your answer about JSON-LD below says you're OK with
> signatures in the graph.

I am very uncomfortable with anything that is different in any way from
current cryptographic practice.  My understanding is that this practice
dictates a strict separation between the thing that is being protected
and the protecting information.   So in a signed document the thing
that is being signed is either separate or is encapsulated.  I was thus
being a bit simplistic in saying that I was OK with appending a
signature - I am only OK with this if there is a separation between the
signature and the thing being signed.  This is decidedly not what
appears to be happening in linked data signatures or in the interface
that you mention.

One of these problems easily shows up when you take the output of the
signining interface and feed it back as input to itself be signed.  The
verifier refuses to verify the signed graph.   That's a major problem -
why should it not be possible to sign and successfully verify a graph
that has a signature in it?   This kind of problem shows up in the
algorithms in https://w3c-ccg.github.io/ld-proofs/

peter
Received on Monday, 14 June 2021 23:44:11 UTC

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