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Re: WebID questions -- was: [dane] Call for Adoption: "Using Secure DNS to Associate Certificates with Domain Names For S/MIME"

From: Ben Laurie <benl@google.com>
Date: Thu, 27 Sep 2012 08:49:50 +0100
Message-ID: <CABrd9SSPb90Z7_5QD6A6QEMjvZM3pE-Q3XOhzxC1aM34PSU_VQ@mail.gmail.com>
To: Kingsley Idehen <kidehen@openlinksw.com>
Cc: Henry Story <henry.story@bblfish.net>, "public-webid@w3.org" <public-webid@w3.org>, Andrei Sambra <andrei@fcns.eu>
On 26 September 2012 23:43, Kingsley Idehen <kidehen@openlinksw.com> wrote:
> On 9/26/12 5:18 PM, Ben Laurie wrote:
>> On 26 September 2012 19:02, Henry Story <henry.story@bblfish.net> wrote:
>>> On 26 Sep 2012, at 19:10, Kingsley Idehen <kidehen@openlinksw.com> wrote:
>>>> On 9/26/12 11:48 AM, Ben Laurie wrote:
>>>>> No, the point you are missing is that in capabilities the_only_
>>>>> authority I need to access a resource is the name of that resource -
>>>>> the URI in your case.
>>>> You can seriously believe I am missing that point while also espousing
>>>> the virtues of hyperlinks as denotation mechanisms for a global web of
>>>> linked data. That doesn't compute. That's a contradiction.
>>>>> Security derives from the unforgeability of the
>>>>> URI, rather than an independent system that decides if some principal
>>>>> has permission.
>>>> Security is not derived from the persistence of a URI, its derived from
>>>> the values exposed directly or indirectly via URI which logic handling
>>>> routing. I can have many identifiers, but relationship semantics ultimately
>>>> determine if I can access a resource at an address, directly or indirectly
>>>> (i.e., name based indirection).
>>> +1
>>> the idea of an unforgeable URI seems gobbledegook to me, frankly. When
>>> people spoke of unforgeable things they spoke of things like diamonds that
>>> could not be copied, swords that were made to such perfection that never
>>> could there be two identical versions of them, etc... A URI is by definition
>>> something that can be copied. In fact there is no way of telling of one URI
>>> is an original or another a copy!
>> This is true, and is one reason it is hard to simulate capabilities using
>> URIs.
> How do you arrive at these conclusions? If you don't mind, have you taken a
> look at the Linked Data meme and what its about? How URIs resolve to
> structured data etc. Basically, you can denote anything entity using a URI.
> Even better is you take advantage of an HTTP URI since you have the power of
> indirection in play such that a denotation resolves to representation. A URI
> becomes an extremely powerful data source name that enables you work wonders
> with structured data. You can simulate all kinds of capabilities via URIs,
> the only limits are:
> 1. our imagination
> 2. our willingness to look at what Linked Data is really about -- forget any
> distracting political wars from the past, it's 2012, let start afresh re.
> AWWW and its capabilities.

Now we're overloading "capabilities" :-)

So, the point is this: object capabilities are a security mechanism,
like ACLs. Their purpose is to restrict access to resources to only
the intended accessors.

With URIs, there are two obvious ways to implement this:

1. Make the URIs unguessable - so, I only get access to the resource
if someone tells me the URI.

2. Link the URI to a public key - so, I only get access to the
resource if I can prove I have the corresponding private key.

The problem with 1 is that the nature of URIs makes it hard to keep
them secret. People like to send them in emails and IMs and they leak
quite easily.

The problem with 2 (which, it should be obvious, fits quite neatly
with WebIDs) is that it requires changes to clients and servers to do
the key proof. Or maybe not, actually ... I guess it could be done at
the back end, wherever you do ACL checks, by instead correlating the
URI and the key presented in the WebID cert.

So ... maybe not such a red herring after all.

Not that this fixes any of the problems I've talked about :-)

>>> The idea of unforgeable URIs, the idea of a web that cannot be linked,
>>> all of these ideas seem to be like weird beasts from a netherworld that
>>> nobody has ever heard of, a Medusa that turns all that look at her into
>>> stone.
>> Not that cannot be linked, but that can only be linked by those you
>> choose to allow to link. The same goal as ACLs, of course.
>> But I should not have introduced the idea, it raises as many questions
>> as it answers. Definitely a red herring. Apologies.
> --
> Regards,
> Kingsley Idehen
> Founder & CEO
> OpenLink Software
> Company Web: http://www.openlinksw.com
> Personal Weblog: http://www.openlinksw.com/blog/~kidehen
> Twitter/Identi.ca handle: @kidehen
> Google+ Profile: https://plus.google.com/112399767740508618350/about
> LinkedIn Profile: http://www.linkedin.com/in/kidehen
Received on Thursday, 27 September 2012 07:50:23 UTC

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