Data and Applications Security Developments and Directions
Dr. Bhavani Thuraisingham
The University of Texas at Dallas

Single-Sign On and Federated Identity Management

November 30, 2009
Single Sign-On
Federated Identity Management

Open ID, Information Card
Single Sign-On
Single sign-on (SSO) is a method of access control that enables a user to log in once and gain access to the resources of multiple software systems without being prompted to log in again.
Single sign-off is the reverse process whereby a single action of signing out terminates access to multiple software systems.
As different applications and resources support different authentication mechanisms, single sign-on has to internally translate to and store different credentials compared to what is used for initial authentication
Single Sign-On
Kerberos based
Initial sign-on prompts the user for credentials, and gets a Kerberos ticket-granting ticket (TGT.)
Additional software applications requiring authentication, such as email clients, wikis, revision control systems, etc, use the ticket-granting ticket to acquire service tickets, proving the user’s identity to the mailserver / wiki server / etc. without prompting the user to re-enter credentials.
Windows environment – Windows login fetches TGT. Active directory-aware apps fetch service tickets, so user is not prompted to re-authenticate.
UNIX/Linux environment – Login via Kerberos PAM modules fetches TGT. Kerberized client applications such as Evolution, Firefox, and SVN use service tickets, so user is not prompted to re-authenticate.
Single Sign-On
Smart card based: Initial sign on prompts the user for smart card. Additional software applications also use the smart card, without prompting the user to re-enter credentials. Smart card-based single sign-on can either use certificates or passwords stored on the smart card
Client Certificate Based: Shared Authentication Schemes which are not Single Sign-On
Single sign on requires that users literally sign in once to establish their credentials. Systems which require the user to log in multiple times to the same identity are inherently not single sign on. For example, an environment where users are prompted to log in to their desktop, then log in to their email using the same credentials, is not single sign on. Shared authentication schemes like OpenID, which require additional sign-on for each web site, are also not single sign on.

Single Sign-On
Enterprise Single Sign-On
Enterprise single sign-on (E-SSO) systems are designed to minimize the number of times that a user must type their ID and password to sign into multiple applications.
The E-SSO solution automatically logs users in, and acts as a password filler where automatic login is not possible. Each client is typically given a token that handles the authentication, on other E-SSO solutions each client has E-SSO software stored on their computer to handle the authentication. On the server side is usually an E-SSO authentication server that is implemented into the enterprise network.

Federated Identity Management
Federated identity, or the òfederation’ of identity, describes the technologies, standards and use-cases which serve to enable the portability of identity information across otherwise autonomous security domains.
The ultimate goal of identity federation is to enable users of one domain to securely access data or systems of another domain seamlessly, and without the need for completely redundant user administration. Identity federation comes in many flavors, including òuser-controlled’ or òuser-centric’ scenarios, as well as enterprise controlled or B2B scenarios.
Federated Identity Management
Federation is enabled through the use of open industry standards and/or openly published specifications, such that multiple parties can achieve interoperability for common use cases.
Typical use-cases involve things such as cross-domain, web-based single sign-on, cross-domain user account provisioning, cross-domain entitlement management and cross-domain user attribute exchange.
Federated Identity Management
Use of identity federation standards can reduce cost by eliminating the need to scale one-off or proprietary solutions.
It can increase security and lower risk by enabling an organization to identify and authenticate a user once, and then use that identity information across multiple systems, including external partner websites.
It can improve privacy compliance by allowing the user to control what information is shared, or by limiting the amount of information shared.
It can drastically improve the end-user experience by eliminating the need for new account registration through automatic òfederated provisioning’ or the need to redundantly login through cross-domain single sign-on.
Federated Identity Management
Leading enterprises around the world have deployed identity federation to get closer with partners, improve customer service, accelerate execution of business partnerships and alliances, cut cost and complexity of integrating outsourced services, and free themselves from vendor lock-in.
End-users and consumer focused web sites are now beginning to engage in identity federation through the adoption of OpenID, which is an open source specification for enabling federation use-cases.
Federated Identity Management
The notion of identity federation is extremely broad, and also evolving. It could involve user-to-user, user-to-application as well as application-to-application use-case scenarios at both the browser tier as well as the web services or SOA (service-oriented architecture) tier.
It can involve high-trust, high-security scenarios as well as low-trust, low security scenarios. The levels of identity assurance that may be required for a given scenario are also being standardized through a common and open Identity Assurance Framework.
It can involve user-centric use-cases, as well as enterprise-centric use-cases. The term òidentity federation’ is by design, a generic term, and is not bound to any one specific protocol, technology, implementation or company.
Federated Identity Management
One thing that is consistent, however, is the fact that òfederation’ does describe methods of identity portability which are achieved in an open, often standards-based manner -meaning anyone adhering to the open specification or standard can achieve the full spectrum of use-cases and interoperability.
Identity federation can be accomplished any number of ways, some of which involve the use of formal Internet standards, such as the OASIS SAML specification, and some of which may involve open source technologies and/or other openly published specifications, (e.g. Information Cards, OpenID, the Higgins trust framework or Novell’ s Bandit project).

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