*Editor’s note: To read Part I of this article, click here. To read Part II of this article, click here

The identity management standards jungle

A critical aspect of the new identity management architecture blueprint I discussed in my previous article is that it needs to be based on a clear separation of identity management concerns. This means that identity and access services – authentication, access control, logging and audit, federation – need to be delivered as shared infrastructure services, governed by a unified policy management layer and underpinned by a federated identity data repository. It also means that these shared identity services should make use of other infrastructure services, such as workflow management, and must be usable by the broader application and IT infrastructure. At the same time the identity and access services, particularly authentication and access control, must be autonomous – to allow entitlements, for example, to be varied in accordance with available authentication facilities.

The upshot of all of this is that the boundaries between the layers of identity management infrastructure are critical to get right. The importance of this is elevated because it is highly unlikely that most organisations will have the luxury of a rip-and-replace strategy or the ability to satisfy all of their identity management requirements with the offerings of a single vendor. Each layer should present a common interface to all services that depend on the functionality of that layer, and open standard protocols and data formats are non-negotiable for those common interfaces to facilitate interoperability.

So where will these standards, which are so important, come from? Today there is a fast-moving and confusing range of standards at differing levels of maturity, focussed on particular identity management capabilities, including:

• Service Provisioning Markup Language (SPML) – focussed on providing standard, technology independent mechanisms for provisioning request and response message exchange. SPML standardises the format of requests to maintain and search provisioning data, as well as to discover information about that provisioning data. However, SPML is yet to receive broad vendor support
• Security Assertion Markup Language (SAML) – focussed on providing standard, technology-independent mechanisms for exchanging security credentials between parties. SAML is based on the notion of assertions, which consist of one or more statements issued by SAML authorities. SAML can be used in web single sign-on scenarios based on HTTP SAML assertion exchange – also called passive – and in application-to-application scenarios based on web services – also called active. SAML is supported by all of the leading identity management vendors
• eXtensible Access Control Markup Language (XACML) – focussed on providing standard, technology independent mechanisms for the definition of authorisation and access control policies, in the form of rules, and their subsequent distribution to the solutions responsible for enforcing them. XACML is yet to receive broad vendor support
• A set of WS-* specifications – a series of web services-based standards focussed on security token format exchange (WS-Trust); the establishment of shared security contexts to enable multiple secure request/response message exchanges (WS-SecureConversation); the definition and exchange, based on WS-Policy, of security policies for use with WS-Security, WS-Trust and WS-SecureConversation (WS-SecurityPolicy); and the federation of identity, attribute, authentication and authorisation information through the coordination of WS-Trust interactions (WS-Federation). The WS-* identity management specifications are supported by many of the leading identity management vendors, particularly IBM and Microsoft
• Liberty Alliance standards – the Liberty Alliance is developing a variety of standards-based initiatives focussed around federated identity management. These initiatives are based on SAML and include ID-FF, which is focussed on human-to-application interaction; and ID-WSF, which is focussed on application-to-application interaction. ID-WSF forms the basis for ID-SIS (Service Interface Specifications), a set of consumer-oriented identity services. These services address requirements such as geo-location, contact data sharing, presence and the sharing of social applications and information, such as bookmarking, blogging and digital photos, by allowing others within their social networks to access those services without their own login. The Liberty Alliance specifications are supported by the majority of the leading identity management vendors, with the notable exception of Microsoft which provides some interoperability through work undertaken with Sun Microsystems
• User-centric identity initiatives – a variety of initiatives are underway focussed on user-centric identity, many of them URL or URI-based, including XRI, XDI, i-names/i-numbers, Light-Weight Identity (LID), OpenID and Yadis (Yet Another Decentralized Interoperability System, focussed on interoperability of URL-based identity systems). Although these are being adopted in the world of online services they have so far received only limited support from vendors focussed on the enterprise identity management market.