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Date: Wed, 4 Jul 2012 21:00:09 +0200
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Subject: Re: Cryptograhically signed docs...
From: Bernhard Gschwantner <bernhard@unserwein.at>
To: "user@couchdb.apache.org" <user@couchdb.apache.org>
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I've been following this thread and like the idea. I may be na=C3=AFve or
completely wrong, but all this sounds quite easy to solve in a design
document and with pure javascript, although probably not very performant.
Just take jens' structure proposal and modify openpgp.js a little bit, put
the stuff into a validate_doc_update function, add the allowed public keys
to a design doc (easy with a couchapp), et voil=C3=A0: you get a completely
replicable and transparent signature checker ;-)

If I find the time tomorrow, I'll take a shot on a proof of concept. The
building blocks are there already...

Cheers,
Bernhard

Am Mittwoch, 4. Juli 2012 schrieb Albin Stig=C3=B6 :

> Sounds interesting.. I think I will take this to the developers mailing
> list and see if I will be able to generate some interest in the idea..
>
> Albin
>
> onsdag den 4. juli 2012 skrev Jan Bot :
>
> > Hi,
> >
> > This would really be a great feature: I'm using CouchDB to manage grid
> > compute jobs and having the ability to sign a document using a private
> key
> > and check it server side with the public key could really make couchdb
> part
> > of the grid infrastructure.
> >
> > Cheers,
> >
> > Jan
> >
> > On Wed, Jul 4, 2012 at 11:17 AM, Albin Stig=C3=B6 <albin.stigo@gmail.co=
m<javascript:;>
> <javascript:;>>
> > wrote:
> >
> > > Hi,
> > >
> > > Jens, thanks for the link. Did you ever finish the app where you were
> > > using these techniques?
> > >
> > > First I naively thought that it would be enough to hash the body of
> > > what you are going to PUT/POST and then sign that hash and include th=
e
> > > signature as a custom http header. I guess this would work for
> > > verifying the data on the first post but you would not be able to
> > > verify the signature later if couchdb does any parsing of the
> > > transported data.
> > >
> > > What you are suggesting using a canonical representation of of JSON
> > > seems like a much better idea it also apparently what oauth uses.
> > >
> > > I guess this would require some hacking on couchdb. It would be reall=
y
> > > neat to have a _keys database much like the _users and for for
> > > documents to have a _signature field. What do you thin..?
> > >
> > > --Albin
> > >
> > >
> > >
> > > On Wed, Jul 4, 2012 at 3:07 AM, Jens Alfke <jens@couchbase.com<javasc=
ript:;>
> <javascript:;>>
> > wrote:
> > > >
> > > > On Jul 3, 2012, at 10:01 AM, Jim Klo wrote:
> > > >
> > > >> Yes, and as a matter of fact, i just got digital signature
> validation
> > > using OpenPGP within a map function working a few minutes ago!
> > > >> Here's a link to the relevant code:
> > >
> >
> https://github.com/jimklo/TheCollector/blob/master/dataservices/thecollec=
tor-resources/views/lib/sig_utils.js
> > > >
> > > > As far as I can tell, this code uses a data schema where the signed
> > > contents are wrapped in some kind of OpenPGP encoding:
> > > >
> > > >>         var msg_list =3D
> > > openpgp.read_message(doc.digital_signature.signature);
> > > >>         for (var i=3D0; i<msg_list.length; i++) {
> > > >>             isValid |=3D msg_list[i].verifySignature();
> > > >>         }
> > > >
> > > > It looks like msg_list is the actual document payload, which has to
> be
> > > decoded using openpgp.read_message.
> > > >
> > > > This is IMHO not a very good solution because it hides the document
> > > contents away =E2=80=94 for example, all the map functions and any ap=
p logic
> that
> > > uses documents will have to know to call read_message, which will als=
o
> > make
> > > them slower.
> > > >
> > > > The schema I implemented (see my previous message) doesn't alter th=
e
> > > basic document format. The signature is in a nested object but applie=
s
> to
> > > the entire document contents (minus the signature itself of course).
> > > There's no need to change any code that reads documents; the only tim=
e
> > you
> > > have to know about the signature scheme is while verifying the
> signature.
> > > It's even possible to have multiple signatures on a document.
> > > >
> > > > =E2=80=94Jens
> > >
> >
>


--=20

Bernhard Gschwantner
Unser Wein G&U OG
Kirchengasse 13/7, 1070 Wien

mobil: +43 (6991) 971 32 96
tel: +43 (1) 971 32 95
e-mail: bernhard@unserwein.at
twitter: @bernharduw <http://twitter.com/bernharduw>
web: www.unserwein.at

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