OpenID

OpenID is a decentralized single sign-on system. Using OpenID-enabled sites, web users do not need to remember traditional authentication tokens such as username and password. Instead, they only need to be previously registered on a website with an OpenID "identity provider". Since OpenID is decentralized, any website can employ OpenID software as a way for users to sign in; OpenID solves the problem without relying on any centralized website to confirm digital identity.

OpenID is increasingly gaining adoption among large sites, with organizations like AOL acting as a provider. In addition, integrated OpenID support has been made a high priority in Firefox 3 and Microsoft is working on implementing OpenID 2.0 in Windows Vista.

History

OpenID was originally developed by Brad Fitzpatrick of LiveJournal, but the term now also includes the Light-Weight Identity, Yadis, Sxip DIX protocol that was proposed at IETF, and XRI/i-names. Future OpenID specifications are being developed in a meritocratic fashion on openid.net, involving many technology companies, user companies and open-source developers.

To help spawn additional deployment, a group of vendors announced a $50,000 USD developer bounty program in August of 2006, offering $5,000 USD each to the first ten large-scale Open Source projects to implement OpenID support.

Currently work is underway developing OpenID Authentication 2.0, which will use the Yadis service discovery protocol. OpenID is now developing into a much more complete framework that will support other identity services besides authentication.

Using OpenID

A basic glossary of the terms used with OpenID:

End user

The person who wants to assert his or her identity to a site.

Identifier

The URL or XRI chosen by the End User as their OpenID identifier.

Identity provider or OpenID provider

A service provider offering the service of registering OpenID URLs or XRIs and providing OpenID authentication (and possibly other identity services). Note that the OpenID specifications use the term "OpenID provider" or "OP".

Relying party

The site that wants to verify the end user's identifier.

Server or server-agent

The server that verifies the end user's identifier. This may be the end user's own server (such as their blog), or a server operated by an identity provider.

User-agent

The program (such as a browser) that the end user is using to access an identity provider or a relying party.

Consumer

An obsolete term for the relying party.

Logging in

A website, such as example.com, which wants to enable OpenID logins for its visitors, places a login form somewhere on the page. Unlike a typical login form, which prompts the user for a user name and password, there is only one field - for the OpenID identifier. The site may choose to display a small OpenID logo next to the field. This form is connected to an implementation of an OpenID client library.

If a user named Alice wants to log in to example.com using the OpenID identifier alice.openid-provider.org that she has registered with the identity provider openid-provider.org, she simply goes to example.com and types alice.openid-provider.org in the OpenID login box.

If the identifier is a URL, the first thing the relying party (example.com) does is transform into a canonical form, e.g., http://alice.openid-provider.org/. With OpenID 1.0, the relying party then requests the web page located at that URL and, via an HTML link tag, discovers that the provider server is, say, http://openid-provider.org/openid-auth.php. It also discovers whether it should use a delegated identity (see below). Starting with OpenID 2.0, the client does discovery by requesting the XRDS document (also called the Yadis document) with the content type application/xrds+xml that may be available at the target URL and is always available for a target XRI.

There are two modes in which the relying party can communicate with the identity provider:

• checkid_immediate, which is machine-oriented and in which all communication between the two servers is done in the background, without the user's knowledge;
• checkid_setup, in which the user communicates with the provider server directly using the very same web browser used to access the relying party site.

The second option is more popular on the Web; also, checkid_immediate can fallback to checkid_setup if the operation cannot be automated.

First, the relying party and the provider (optionally) establish a shared secret - an associate handle, which the relying party then stores. If using checkid_setup, the relying party redirects the user's web browser to the provider. In this case, Alice's browser is redirected to openid-provider.org so Alice can authenticate herself with the provider.

The method of authentication may vary, but typically, an OpenID provider asks for a password (and then possibly stores the user's session using cookies, as many websites with password-based authentication do). Alice may be prompted for her password if she was not logged in on openid-provider.org, and then asked whether she trusts, say, http://example.com/openid-return.php - the page designated by example.com as the one where the user should return after completing authentication - to receive details about her identity. If she answers positively, OpenID authentication is considered successful and the browser is redirected to the designated return page with credentials given. If Alice decides not to trust the relying party site, the browser is still redirected - however, the relying party is notified that its request was rejected, so example.com refuses to authenticate Alice in turn.

However, the login process is not over yet because at this stage, example.com cannot decide whether the credentials received really came from openid-provider.org. If they had previously established a shared secret (see above), the relying party can validate the shared secret received with the credentials against the one previously stored. Such a relying party is called stateful because it stores the shared secret between sessions. In comparison, a stateless or dumb relying party must make one more background request (check_authentication) to ensure that the data indeed came from openid-provider.org.

After Alice's identifier has been verified, she is considered logged in to example.com as alice.openid-provider.org. The site may then store the session or, if this is her first logon, prompt Alice to enter some information specific to example.com, in order to complete registration.

OpenID does not provide its own form of authentication, but if an identity provider uses strong authentication, OpenID can be used for secure transactions such as banking and e-commerce.

Identifiers

Starting with OpenID Authentication 2.0 (and some 1.1 implementations), there are two types of identifiers that can be used with OpenID: URLs and XRIs.

There are two ways to obtain an OpenID-enabled URL that can be used to login on all OpenID-enabled websites.

1. To use an existing URL that one's own control (such as one's blog or home page), and if one knows how to edit HTML, one can insert the appropriate OpenID tags in the HTML code following instructions at the OpenID specification.
2. The second option is to register an OpenID identifier with an identity provider. They offer the ability to register a URL (typically a third-level domain) that will automatically be configured with OpenID authentication service.

XRIs are a new form of Internet identifier designed specifically for cross-domain digital identity. For example, XRIs come in two forms—i-names and i-numbers—that are usually registered simultaneously as synonyms. I-names are reassignable (like domain names), while i-numbers are never reassigned. When an XRI i-name is used as an OpenID identifier, it is immediately resolved to the synonymous i-number (the CanonicalID element of the XRDS document). This i-number is the OpenID identifier stored by the relying party. In this way both the user and the relying party are protected from the user's OpenID identity ever being taken over by another party as can happen with a URL based on a reassignable DNS name.

Adoption

As of July 2007, there are over 120 million OpenID's on the Internet (see below) and approximately 4,500 sites have integrated OpenID consumer support.

America Online provides (brokers) OpenIDs, in the form "openid.aol.com/screename".

idproxy.net provides OpenIDs for Yahoo! users via Yahoo!'s authentication API (BBAuth); idproxy.net was created by a former Yahoo! developer but is not otherwise related to the company.

Orange offers OpenIDs to their 40 million broadband subscribers.

Six Apart blogging hosts LiveJournal and Vox. Both support OpenID; Vox as a provider and LiveJournal as both a provider and a relying party.

Other services accepting OpenID as an alternative to registration include Wikitravel, photo sharing host Zooomr, linkmarking host Ma.gnolia, identity aggregator ClaimID, icon provider IconBuffet, Basecamp and Highrise by 37signals, and Jyte.

OpenID Enabled lists many more sites, services, and platforms.

OpenID Foundation

The OpenID Foundation is a 501(c)3 non-profit incorporated in the United States. The OpenID Foundation was formed to help manage intellectual property, marketing efforts and other activities related to the success of the OpenID community. The singular goal of the OpenID Foundation is to protect OpenID so that it may be used by any and all that want to.

People

The OpenID Foundation Board of Directors has seven members:

• Scott Kveton (MyStrands)
• David Recordon (Six Apart)
• Dick Hardt (Sxip)
• Martin Atkins
• Artur Bergman (Wikia)
• Johannes Ernst (NetMesh)
• Drummond Reed (Parity and OASIS XRI and XDI TCs)

and an Executive Director:

• Bill Washburn (Ph.D.)

and an European Representative:

• Snorri Giorgetti (OpenID Europe)

The European counterpart OpenID Europe was founded on June, 2007. It is a non-profit organization to help promote and deploy the OpenID framework in Europe. OpenID Europe is independent of the OpenID Foundation. The organisation's headquarters are in Paris.

Legal issues

R-Objects Inc. filed for the OpenID trademark (serial 78899244) on 2 June 2006 which was published for opposition on 9 January 2007, claiming a first use date of 17 May 2005 and a first use in commerce date of 18 April 2006. Sxip Identity Corporation subsequently filed for the OpenID trademark (serial 77041930) on 11 November 2006 but abandoned it on 23 November 2006. Randy "ydnar" Reddig claimed ownership of the OpenID logo on 29 June 2005 and announced plans to transfer it to Six Apart (or some OpenID.org).

There is a pending USPTO patent application with PCT priority from Denmark of March 9 2001 that covers the central aspects of OpenID.

Six Apart Ltd. are the registrant for the "official" openid.net domain, which was transferred from David I. Lehn on 16 June 2005.

The official site currently states:

Nobody should own this. Nobody's planning on making any money from this. The goal is to release every part of this under the most liberal licenses possible, so there's no money or licensing or registering required to play. It benefits the community as a whole if something like this exists, and we're all a part of the community.

Both Sun Microsystems and VeriSign have issued patent non-assertion covenants covering OpenID 1.1 specifications. These covenants state that neither company will assert any of their patents against OpenID implementations and will revoke their promises from anyone who threatens, or asserts, patents against OpenID implementors.

Criticism

Some observers have suggested that OpenID has security weaknesses and may prove vulnerable to phishing attacks.

For example, a malicious relying party may forward the end user to a bogus identity provider authentication page asking that end user to input their credentials. On completion of this, the malicious party (who in this case also control the bogus authentication page) could then have access to the end user's account with the identity provider, and as such then use that end user’s OpenID to log into other services.

In an attempt to combat possible phishing attacks some OpenID providers mandate that the end user needs to be authenticated with them prior to an attempt to authenticate with the relying party. However this then relies on the end user knowing the policy of the identity provider, and regardless this issue remains a significant additional vector for man-in-the-middle phishing attacks.

Other criticisms are that the addition of a 3rd party (the identity provider) into the authentication process significantly adds complexity and therefore possibility of vulnerability into the system. Also this system shifts responsibility for "quality" of authentication to the end user (in their choice of identity provider), a shift that the end user and the relying party (for example their bank) need to understand.

See also

• Identity Centric Architecture
• Identity 2.0
• Light-Weight Identity
• Windows CardSpace
• Liberty Alliance
• Shibboleth (Internet2)
• Athens access and identity management
• Extensible Name Service
• SAML
• WS-Federation

References

• The Case for OpenID — ZDNet article contrasting OpenID with other identity systems by Johannes Ernst (NetMesh) and David Recordon (VeriSign)
• OpenID: The RESTful approach to Single Sign-On - brief overview
• OpenID for non-SuperUsers - by Sam Ruby

External links

• OpenID official site
• OpenID Source (OIDS) — OpenID Source Initiative is a Community in the OID community to grow OpenID
• identity.eastmedia.com — OpenID and Identity info at eastmedia
• OpenID Enabled — resource for OpenID users and developers
• Directory of OpenID enabled Websites (Consumers)
• OpenID Europe European OpenID Foundation that promoting OpenID in Europe.
• OpenID protocol overview and OpenID4Java library example
• An interview with Simon Willison about OpenID