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+ <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
+ <meta property="dc:subject" content="identity, WebID, authentication, Browser, REST, HTTPS, Public-key cryptography" />
+ <title>The WebID Protocol & Browsers</title>
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+</head>
+
+<body>
+ <h1 property="dc:title">The WebID Protocol & Browsers</h1>
+ <div class="description">
+ <p datatype="" property="dc:description">Position Paper for <a href=
+ "http://www.w3.org/2011/identity-ws/">W3C Workshop on Identity in the Browser</a>
+ 24/25th May 2011, Mountain View (USA)</p>
+
+ <p>Presented by members of the <a href=
+ "http://www.w3.org/2005/Incubator/webid/">
+ W3C WebID Incubator Group</a></p>
+
+
+ <p class="headerish"><strong>Authors</strong>:</p>
+ <ul class="authorship" rel="dc:creator">
+ <li typeof="foaf:Person">• <a rel="foaf:homepage" href="http://jeffsayre.com/" property="foaf:name">Jeff Sayre</a></li>
+ <li about="http://bblfish.net/#hjs" typeof="foaf:Person"><a rel="foaf:homepage" href="http://bblfish.net/" property="foaf:name">Henry Story</a>, WebID Incubator Chair</li>
+ </ul>
+
+ <p class="headerish"><strong>Contributors</strong>:</p>
+ <ul class="authorship" rel="dc:contributor"><li typeof="foaf:Person">•
+ <a rel="foaf:workInfoHomepage" href="http://www.cs.kent.ac.uk/people/staff/dwc8/" property="foaf:name">David Chadwick</a>, University of Kent</li>
+ <li about="http://openspring.net/scor#me" typeof="foaf:Person"><a rel="foaf:homepage" property="foaf:name" href="http://openspring.net/scor">Stéphane Corlosquet</a></li>
+ <li typeof="foaf:Person"><a rel="foaf:workInfoHomepage" property="foaf:name" href="http://vsr.informatik.tu-chemnitz.de/people/gaedke/">Martin Gaedke</a>, Chemnitz University of Technology</li>
+ <li typeof="foaf:Person"><a rel="foaf:blog" property="foaf:name" href="http://www.openlinksw.com/blog/~kidehen/">Kingsley Idehen</a>, OpenLink Software</li>
+ <li typeof="foaf:Person"><a rel="foaf:homepage" property="foaf:name" href="http://apassant.net/alex">Alexandre Passant</a>, DERI, NUI Galway</li>
+ <li about="http://fcns.eu/people/andrei/card#me" typeof="foaf:Person"><a rel="foaf:homepage" property="foaf:name" href="http://fcns.eu/">Andrei Sambra</a></li>
+ <li typeof="foaf:Person"><a rel="foaf:workInfoHomepage" href="http://ii.uwb.edu.pl/~dtomaszuk/" property="foaf:name">Dominik Tomaszuk</a>, <a rel="foaf:workplaceHomepage" href="http://ii.uwb.edu.pl/">University of Bialystok</a></li>
+ <li typeof="foaf:Person"><a rel="foaf:made" property="foaf:name" href="http://portal.acm.org/citation.cfm?id=560938">Peter Williams</a></li>
+ </ul>
+ </div>
+
+ <h2>1. Position Statement</h2>
+
+
+ <p>The browser is both the interface to the
+ Web as well as presenting the user's face to the world. The browser user should
+ therefore be conscious of the face he is presenting at any time. He should be able to
+ change it easily: identity selection should be a one-click gesture,
+ cryptographically-secure, and web site independent. It should put the user in control
+ of the information he shares with each site. And it should be available
+ now.</p>
+
+
+ <p>The WebID protocol enables all of the
+ above. It works in all browsers that correctly implement HTTPS and client-side
+ certificates. But with a twist: it ties those certificates into the web in a
+ <a href="http://www.ics.uci.edu/~fielding/pubs/dissertation/top.htm">RESTful manner</a> allowing identities to be linked together in
+ a secure social web of trust, that does not require central authorities, and that
+ allows the user to control how he describes himself to each site he logs
+ into.</p>
+
+
+ <p>After describing the WebID protocol and its benefits, we will suggest a roadmap for future improvements in the browser that can take advantage of it.</p>
+
+
+ <h2>2. WebID Overview</h2>
+
+ <p>To illustrate how WebID works, we will first look in detail at what happens on the wire when Bob connects for the first time to a protected resource on Alice's Web Server. This resource could simply be a login button, or it could be any of the resources published there. This should help show just how simple and efficient the protocol is: it requires only one more HTTP connection than the original resource
+ requested, and the results of this connection can be cached. </p>
+
+ <ol>
+ <li>Bob requests
+ Alice's protected HTTPS resource</li>
+ <li>Alice's web
+ server requests the client certificate on the TLS connection started above</li>
+ <li>Bob's browser
+ presents him with a selection of identities to choose from: <div class="figure"><img width=
+ "576" height="235" src="webid_images/image001.jpg" alt="" /></div>Having selected one, the corresponding X509
+ certificate is sent to Alice's server:
+ <pre> Public Key Info:
+ Public Key Algorithm: rsaEncryption
+ Public-Key: (1024 bit)
+ Modulus:
+ 00:e8:f9: [snip] :c6:af:2e
+ Exponent: 65537 (0x10001)
+ X509v3 extensions:
+ X509v3 Subject Alternative Name:
+ URI: <span class="highlight">https://bob.net/id/bob#me</span></pre>
+ It contains Bob's WebID, shown in bold red above.</li>
+ <li>Alice's server:<ol>
+ <li>checks that
+ Bob's browser is in possession of the private key corresponding to the public key
+ sent in the certificate, as specified by TLS</li>
+ <li>extracts the
+ URI from the Subject Alternative Name field of the certificate, which is known as
+ Bob's WebID: a global identifier that refers to Bob via a document that describes
+ him, in a machine readable way using W3C standards.<div class="figure"><img width="708" height="544" src=
+ "webid_images/WebIDSequence-friendly.jpg" alt="" /></div></li>
+ </ol></li>
+ <li>Alice's server
+ fetches Bob's WebID Profile at https://bob.net/id/bob in the example if an up to date
+ version is not in the cache</li>
+ <li>Alice's server
+ checks that the profile relates Bob's WebID to the public key found in the
+ certificate. If they match then she knows that she is in
+ communication with the agent referred to by https://bob.net/id/bob#me</li>
+ <li>Bob's identity
+ is then checked as to its position in a graph of relations in order to determine
+ trust according to some criteria decided by Alice combined with information from the
+ cloud.<br/>
+ This is outside the core of WebID, but it is important to
+ understand how it can work. Alice might decide for example that only a group of
+ friends who have given her a WebID personally may have access. Or she may be more
+ lenient, and allow any of the <a href="http://xmlns.com/foaf/0.1/">friends of those friends</a> to also access that
+ resource, as specified by them in their profile located on their servers. Or she may
+ only trust employees of her company, or of her department, to view that resource.
+ Alice's server can do a lookup in a local file, crawl the web at intervals, or use
+ web services to gather the data to help make that decision.</li>
+ <li>Access is
+ granted fully, partially, or denied and a representation is returned. Assuming the
+ resource requested is a friend graph, a full representation could be returned to a
+ friend, and a very limited one to an anonymous user.</li>
+ </ol>
+
+ <p>The WebID placed in the X509 Certificate can be a https URL as
+ shown above. Although the HTTPS scheme is currently the most widely implemented,
+ WebID could also used with any dereferenceable scheme such as ftps://, ldaps://,
+ xris://, accnt: (used by <a href="http://code.google.com/p/webfinger/">webfinger</a> ). It could also be used in future schemes such as
+ <a href="http://lists.w3.org/Archives/Public/public-xg-webid/2011Mar/0068.html">
+ httpk</a> that would give up human readable URIs in order to
+ avoid the centralisation problems of DNS.</p>
+
+
+ <h2>3. Advantages of WebID</h2>
+
+
+ <p>Issues of identity and privacy have been
+ growing increasingly serious as the Web has become social over the last decade.
+ Remembering login details has grown into a serious security issue as more sites asked
+ for them than people had the ability to remember. And the inability to easily share
+ restricted information across websites has become a visible problem to 100s of
+ millions of people as they started finding themselves and those they wished to
+ communicate with split across siloed services.</p>
+
+ <p>Specifically, WebID offers the following
+ advantages.</p>
+
+
+ <h3>3.1 Overcoming Password Fatigue</h3>
+
+
+ <p>Passwords are <em>difficult</em> to remember or
+ they are easy to crack. As a result people tend to re-use them, making phishing
+ attacks the biggest threat on the web, leading to a mistrust of new services. WebID
+ uses TLS-client certificates and public key cryptography as shipped in current
+ browsers in a way that enables the same certificate to be used across sites securely.
+ Furthermore with the HTML5 supported <code>keygen</code> element, creating such a certificate is
+ as easy as submitting an HTML form.</p>
+
+
+ <h3>3.2 OpenID</h3>
+
+
+ <p><a href="http://openid.net/">OpenID</a>
+ reduces the account multiplication issue by allowing users to login
+ to every site using the same global identifier. This provides a base from which WebId can be deployed,
+ procuring the following extra advantages:</p>
+
+ <ul>
+ <li><strong>Protocol
+ simplicity</strong>: the WebID protocol is a lot simpler,
+ requiring only one more connection over and above the connection to the requested
+ resource, where the result is cacheable. OpenID <a href=
+ "http://blogs.sun.com/bblfish/entry/the_openid_sequence_diagram">requires seven TLS connections</a>, significantly more than WebID. These
+ additional steps create opportunities for denial of service attacks, making it more
+ difficult to secure and to debug.</li>
+ <li><strong>User-interaction
+ simplicity</strong>: OpenID requires the user to remember and type
+ an OpenID URL. WebID hides this in the X509 certificate allowing the browser to offer
+ select-and-click interaction. This is very helpful anywhere, but especially on
+ <a href="http://blogs.sun.com/bblfish/entry/one_click_global_sign_on">handheld devices</a>.</li>
+ </ul>
+
+<p>These protocol simplifications create a cascade of additional benefits. WebID can be applied recursively, enabling the Relying Party (Alice above) to identify herself using WebID, making it easy to <a href="http://blogs.sun.com/bblfish/entry/sketch_of_a_restful_photo">build an authorisation protocol</a>. WebId takes full advantage of the peer to peer nature of the Web. </p>
+
+ <h3>3.3 Public Key Infrastructure</h3>
+
+
+ <p>TLS-client certificates have been available in
+ the browser since 1996, but their usage has been limited to a small number of sites.
+ The organisation which generates the certificate is usually the same as the one that
+ consumes it, giving the user little advantage over username/passwords layered on
+ server-side https. Outside of very large and well-funded Defence related
+ organisations, client-side certificates have thus had very poor adoption.</p>
+
+ <p>The missing link to wide adoption is the global naming system
+ that OpenID takes advantage of with URLs, and that allows one to potentially
+ authenticate to all sites. What failed TLS was that X500 names were not Universal
+ Identifiers, were not designed to form an interlinked web, and hence were not usable
+ to authenticate to sites without those first having a federated agreement. One can easily
+ imagine how much resistance there would have been to global hypertext system if organisations had
+ to first make an agreement with every web site they wanted to visit, before their users
+ were able to visit them. </p>
+
+ <p>Having solved the naming/identity problem using standard URLs, WebId authorization agents can then use the web of interlinked profiles and other resources (eg. academic publications, ...) to calculate trust in a dynamic manner. Since trust can then be spread to a much large network of actors, each bringing a small piece of information to the graph, this allows both greater resilience in the system and more flexibility.</p>
+
+
+ <h3>3.4 Future Proof Protocol</h3>
+
+ <p>Not only does WebID work with the Web as it is
+ today, but it will be strengthened with the rollout of critical infrastructure
+ elements such as DNSSEC, which can be used as <a href=
+ "http://www.wired.com/techbiz/people/magazine/16-12/ff_kaminsky?currentPage=all">Dan Kaminsky</a>
+ explains in his <a href="http://dankaminsky.com/2010/12/13/dnssec-ch1/">DNSSEC Diaries</a>
+ to publish public keys of services, a work being developed formally
+ by the <a href=
+ "http://datatracker.ietf.org/wg/dane/charter/">
+ IETF Dane</a>
+ working group. This can be used to increase trust in all server
+ certificates, but in particular self-signed server certificates, which according to a
+ report by the <a href=
+ "http://www.eff.org/observatory">
+ EFF Observatory</a>
+ are three times more numerous than CA-signed certificates. By
+ lowering the entry barrier to using cryptography, both WebID and Dane will help bring
+ about an increasingly-secure Web.</p>
+
+ <h2>4. Recommended Browser Improvements</h2>
+
+ <p>All current browser-based authentication
+ methods fail to give full control over identity to the user. We declare that browsers
+ MUST give the user full visible control of their identity. With TLS, as with cookies,
+ one should be able to see clearly which identity one is logged in under and be able
+ to easily become anonymous again, as far as that is possible of course. The Firefox
+ Weave team have shown what this could look like, making use of the URL bar's existing
+ role as guarantor of server identity and extending it to client identity.</p>
+
+ <div class="figure"><img width="278" height="157" src=
+ "webid_images/image003.jpg" alt="" /><img width="337" height="202" src=
+ "webid_images/image004.jpg" alt="" /></div>
+
+ <p>Here the user can see what persona they are
+ presenting to the site or if they are anonymous. It also permits the user to change
+ identity or to log out. The browser could then make use of the information found in
+ the WebID profile--linked to from the X509 certificate--such as finding a link to a
+ picture which could then be displayed, or linking to the account management page as
+ shown above.</p>
+
+ <p>This WebID anchor can then be used by browsers
+ to improve the user experience by:</p>
+ <ul>
+ <li>using bookmarking
+ services linked to from the profile</li>
+ <li>using the linked social
+ graph to provide real time changes to address books as well as social web based spam
+ protection</li>
+ <li>building micropayment
+ services by using the TLS cryptography layer, ...</li>
+ </ul>
+
+ <h2>5. Conclusion</h2>
+
+ <p>WebID allows users to authenticate easily and
+ securely to any website in the world in a one click gesture without needing to fill
+ out any new forms. That site can immediately personalise the experience given the
+ information and social graph made available to it by the user (see <a href="http://blogs.sun.com/bblfish/entry/sketch_of_a_restful_photo">Sketch of a RESTful photo Printing service</a> ). This will allow innumerable applications
+ to be built that improve relations between individuals and their friends, co-workers,
+ employers, and vendors across domain and organisational boundaries.</p>
+
+ <p>The <a href="http://www.w3.org/2005/Incubator/webid/">
+ W3C WebID Incubator Group</a>
+ is keen to work with browser vendors and Web service providers to
+ help standardise the necessary formats, semantics, and RESTful protocols and to provide test suites for these. We are also keen to work with the <a href="http://www.w3.org/2005/Incubator/federatedsocialweb/">Federated Social Web XG</a> to build interoperable services in order to discover what gets adopted, standardise those pieces that are most widely agreed on, and discover issues that require longer term research to be resolved.</p>
+
+ <h2>6. Additional Resources</h2>
+ <ul>
+ <li><a href=
+ "http://www.w3.org/2005/Incubator/webid/spec/">
+ WebID Draft Spec</a></li>
+ <li><a href=
+ "http://www.w3.org/wiki/Foaf%2Bssl/FAQ">
+ WebID Frequently Asked Questions</a></li>
+ <li><a href=
+ "http://www.w3.org/wiki/Foaf%2Bssl">WebID Wiki</a></li>
+ </ul>
+
+
+</body>
+</html>