Patent Publication Number: US-8117649-B2

Title: Distributed hierarchical identity management

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a Divisional of and claims priority to U.S. Non-Provisional patent application Ser. No. 10/455,438, filed Jun. 6, 2003 which claims the benefit of and priority to U.S. Provisional Application Ser. No. 60/386,256 filed on Jun. 6, 2002, the disclosures of which are incorporated herein by reference as if set forth in their entirety for all purposes. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to a method and system for identity management. More particularly, the present invention relates to a distributed hierarchical identity management system and method if its use in distributed computer networks. 
     BACKGROUND OF THE INVENTION 
     In the field of electronic commerce there is an acknowledged need for a system and method to either manage or authenticate identity based information. It is acknowledged among those skilled in the art that the authentication of identity based information is not related to guaranteeing that a user is who he or she says. Instead, authentication of identity is restricted to authenticating that a user has presented the same credentials that were previously presented when an identity was asserted. A simple way to understand this subtle difference is to examine a situation where a user is identified by a user identification (user ID) to which there is an associated password. An electronic system has no way of determining who the user is when an account is initialized. However, after the account is initialized the presentation of the user ID and password in combination can be taken as proof that this is the same person who had previously registered for a service and provided these credentials. The presentation of a user ID and password does not prove that the user is a particular individual. 
     Identity management is of great concern in the electronic commerce field because it allows an electronic vendor or service provider to provide a user with customized services and further allows the vendor to track user behaviour. From the user perspective, identity management permits a user to retrieve previously stored identifying information. In the absence of any identity management system each individual use of a service would be accompanied by selecting a series of settings that could not be maintained in the following session. For example, in the case of an on-line purchase the lack of an identity management system would entail requiring a user to provide all identifying information, including credit card numbers, billing and shipping addresses for each and every purchase. This is commonly regarded as a nuisance to consumers, and serves as a detriment to on-line commerce. 
     One skilled in the art will appreciate that though the following discussion generally relates to electronic commerce applications of identity management, a number of other non commerce related services, such as customisation of a news site, registration for access to a newspaper, and maintenance of a desired display configuration for an electronic discussion site, all make use of identity management. For these services the ability of a user to have a single-sign on for multiple services is a high priority. 
       FIG. 1  illustrates a first generation identity management system. A user  100  connects over internet  102  to an electronic retailer  104 , commonly referred to as an E-tailer. E-tailer  104  is typically accessed using a hypertext transfer protocol (HTTP) session. Upon an initial visit to a site hosted by E-tailer  104 , user  100  creates a user profile including a user ID and password. The user ID and password, along with other associated information, potentially including credit card information, shipping and billing addresses, and display preferences, are stored in user profile database  106 . Preferably, user profile database  106  is inaccessible to general computers connected to internet  102  to protect the confidential user information. After creating a user profile in user profile database  106 , user  100  can simplify further visits to E-tailer  104  by simply presenting a credential to certify his or her identity. Typically, this credential is a combination of the user ID and password. Upon being presented with this credential, E-tailer  104  can perform a look-up in the user profile database  106  to confirm that user  100  has presented a valid identity credential. Upon successful completion of this check, user  100  will not be prompted to provide already known information. From the perspective of E-tailer  104 , this system ensures that user  100  has provided all information required for transactions, which can then be stored in the user profile database  106 . This information can be correlated across a number of sessions or transactions to create user profile trends. From the perspective of a user, this system permits simplified dealings with E-tailer  104 . However, a drawback to this system is illustrated in  FIG. 2 . 
       FIG. 2  illustrates the network model of user  100  connecting, using internet  102 , to two different E-tailers, E-tailer  104   a  and E-tailer  104   b . Each E-tailer has its own user profile database: databases  106   a  and  106   b , respectively. Because the user ID and password is used to authenticate the identity of user  100 , E-tailers typically insists that each user ID be unique. Thus, it is conceivable that user  100  may have different user IDs at E-tailer  104   a  and  104   b , in addition to further user IDs at other E-tailers not shown. Multiple user Ids are difficult to manage from the perspective of the user. Additionally, if the user&#39;s information changes, for example if user  100  moves or changes credit card information, each user information database  106   a  and  106   b  must be independently updated. Though on a small scale this is merely troublesome, for many users who frequent a variety of E-tailers this can be a great nuisance. Additionally, repeated entry of user data increases the probability that the user will inadvertently provide incorrect information, which is a detriment to the E-tailer. Thus in combination, the responsibility of ensuring the data integrity of a number of databases, and the hassles associated with multiple user IDs render this model of identity management lacking in the eyes of many users. 
     To ensure a unique user ID, many E-tailers use the e-mail address of user  100  in place of a user ID. However, the e-mail address provided by the user is not guaranteed to be static over any length of time. In many cases, users are provided e-mail addresses by employers, internet service providers, or free e-mail providers. In all of these cases, it cannot be guaranteed that a user will not change an e-mail address due to a change in employment, a change in an internet service provider, or simple whim. As a result, users are required to resubscribe to E-tailers when their e-mail address changes. 
     To ensure that a user can use a single user ID for a plurality of services, and to provide what is commonly referred to in the art as “single sign-on”, a second generation identity management and authentication solution was created. This solution is typically referred to as a hierarchical identity management system, and is typified by Microsoft&#39;s Passport™ service. An overview of this model is provided in  FIG. 3 . 
       FIG. 3  illustrates user  100  having a connection to identity provider  108  (IDP), preferably over internet  102 . User  100  provides IDP  108  with a set of identity based information which is associated with a unique user ID and password combination. This information is stored in user profile database  110 . When user  100  connects to an E-tailer  112  which is affiliated with IDP  108 , user  100  provides E-tailer  112  with identity credentials that are transmitted to IDP  108  to authenticate user  100 . Typically, the credentials provided by user  100  to IDP  108  through E-tailer  112  are a user ID and password combination. Upon authentication of user  100 , IDP  108  provides E-tailer  112  with the stored identity information. Typically, the information provided by IDP  108  to E-tailer  112  is either a strictly defined subset of the information stored by IDP  108 , or is the entire collection of data associated with user  100  stored by IDP  108  in user profile database  110 . Because IDP  108  stores information that can be accessed by a plurality of E-tailers with whom it is affiliated IDP  108  typically does not store site specific information, such as preferences a user has expressed on a particular site, nor does IDP  108  use user preference database  110  to store a history of any items purchased by user  100  at a given E-tailer. As a result, E-tailer  112  must maintain a separate user preference database  114 . The information in user preference database  114  is used to track the patterns of user  100 , and to maintain a purchase, or subscription history, for user  100 . 
     An exemplary transaction in this model entails user  100  requesting a web page from E-tailer  112  using an HTTP link over internet  102 . During this HTTP session user  100  indicates that he wishes to purchase a number of items. During a check-out type procedure E-tailer  112  asks user  100  to authenticate identity. In order to receive authentication from IDP  108 , E-tailer  112  requests and receives from user  100  the credentials required for authentication which are then passed to IDP  108  and authenticated. In an alternate embodiment, user  100  does not provide E-tailer  112  with authentication information. Instead, when E-tailer  112  requires authentication of identity, it redirects user  100  to IDP  108  and upon completion of this transfer user  100  provides the IDP  108  with the authentication information required. Upon successful authentication of user  100 , IDP  108  redirects user  100  back to E-tailer  112 . Using either the same, or a different, data communication channel, IDP  108  provides E-tailer  112  with the information stored in user profile database  110 . This information is then correlated with information stored in user preference database  114  to ensure that user  100  can access historical information. 
     This model of identity management addresses the single sign-on problems associated with the first model of identity management, however, a number of other issues are introduced. A first problem is the trustworthiness of the entity running IDP  108 . This entity must be trusted by both E-tailer  114  and user  100 . IDP  108  must be trusted by user  100  to safeguard information and to provide that information only to entities approved by user  100 . E-tailer  112  must trust IDP  108  to provide reliable service, accurate data, and to not act in a predatory manner. If E-tailer  114  is a service provider that offers a service competing with a service offered by the entity running IDP  108 , E-tailer  114  will typically not have a high level trust in IDP  108 . 
     As a result of many privacy concerns among users, the Microsoft Passport™ service is implemented in such a manner that a user is never required to provide E-tailer  114  with identity authentication information. Instead re-direction commands are used to pass a user from E-tailer  114  to IDP  108  over a secure connection. Over this secure connection, user  100  provides IDP  108  with identity authentication information. Upon authenticating user  100 , IDP  108  redirects user  100  back to E-tailer  112  and provides E-tailer  112  with authentication and user information in a secure back channel. To ensure that two E-tailers cannot correlate the information about a single user  100  at different sites, IDP  108  provides E-tailer specific identity coding which prevents E-tailers from using the identity coding index to correlate a user between two sites. However, one skilled in the art will appreciate that E-tailer  114  typically has a credit card number associated with user  100 , and thus two E-tailers sufficiently motivated to share information could correlate their databases using credit card information, email addresses, or home addresses, as a cross-referencing field. 
     The present embodiment of Microsoft&#39;s Passport™ system has failed to gain sufficient traction in the electronic commerce marketplace to dislodge the first generation of identity management systems. One reason for this is that a centralized user profile database such as user profile database  110  typically has a static data schema. That is it has a predefined set of information that it stores. However, different E-tailers typically request different sets of information from a user. Because a centralized user profile database  110  is not designed to store all information that a variety of E-tailers require, many E-tailers have determined that it is not worth their while to transition to a centralized user profile database  110  such as that offered by Microsoft&#39;s Passport™ service. Another reason for the inability of the Passport™ service to displace first generation identity management systems is user wariness in providing a single entity with vast amounts of identity information. In order for a user to trust an IDP sufficiently to provide this amount of information, a pre-existing trust relationship, and a user assumption of the security of the data must be present. As many users have not had a historical relationship with Microsoft of this type, many users are very reluctant to provide this information. 
     Another concern among many parties is that a hierarchical identity management system promotes monopolistic tendencies. To address these concerns a third generation model of identity management system has been created by the Liberty Alliance. This model can best be described as a distributed identity management system. Such a system is illustrated in  FIG. 4 . 
       FIG. 4  illustrates the distributed identity management system proposed by the Liberty Alliance. This specification describes a plurality of identity providers, here illustrated as IDP 1   116 , IDP 2   120  and IDP 3   124 , having user profile databases UPD 1   118  UPD 2   122  and UPD 3   126 , respectively. All IDPs exist in a web of trust  128  where each IDP has a trust relationship with every other IDP, trust relationships are shown in dash lines. To provide data security, communication between IDPs in web of trust  128  is done using asymmetric encryption. Thus, in the example of  FIG. 4 , IDP 1   116  has a public and private encryption key associated with it, as do IDP 2   120  and IDP 3   124 . IDP 1   116  also has the public keys of IDP 2   120  and IDP 3   124 . Thus, all requests directed between two IDPs can be encrypted using the public key of the destination IDP and can be signed using the private key of the transmitting IDP. Thus, if IDP 1   116  needs to communicate with IDP 2   120 , it encrypts the request to using the public key assigned to IDP 2   120  and signs the encrypted message using its own private key. IDP 2   120  is able to de-crypt the encrypted message using its private key, and verify the signature of IDP 1   116  using the public key assigned to IDP 1   116  stored in IDP 2   120 . This ensures that each IDP in web of trust  128  is able to communicate with every other IDP in the web of trust without fear that the data channel between IDPs has been compromised. User  100  registers with one of the IDPs in web of trust  128 , as shown in  FIG. 4 , user  100  is associated with IDP 3   124 . IDP 3   124  stores identity information provided by user  100 , along with identity credentials in UPD 3   126 . When user  100  establishes a session with an E-tailer associated with any of the IDPs in web of trust  128 , such as E-tailer B  132 , user  100  can provide E-tailer B with identity credentials that will then be provided to one of the systems in web of trust  128 . As illustrated in  FIG. 4 , E-tailer B  132  is affiliated with IDP 2   120 . Thus, ID credentials of user  100  are presented to E-tailer B  132 , which relays them to IDP 2   120 . To authenticate user credentials of user  100 , IDP 2   120  determines that user  100  is affiliated with IDP 3   124  and thus creates a secure data connection using public and private data keys between itself and IDP 3   124 . This data connection is used to authenticate the identity credentials provided by user  100 . Upon authenticating user  100 , IDP 3   124  provides IDP 2   120  with identity information which is then relayed back to E-tailer B  132 . 
     This system provides the user  100  with a single sign-on capability and addresses the concerns related to monopolistic tendencies of an IDP. Because each IDP is independent of other IDPs, it is not considered a global storehouse of information. Thus, if an IDP security is breached only the information associated with that IDP&#39;s user profile database is comprised. This is an advantage over the hierarchical model where comprise of the user profile database exposes all users in the system. 
     However, according to the specification of the Liberty Alliance, only a defined set of user identity information is stored at the IDPs. Thus, E-tailers must still question user  100  about information not stored by an IDP. Additionally, public and private encryption keys require each IDP to be able to perform numerous computation intensive tasks for each data request. Additionally, a sophisticated key management system must be employed as the size of the web of trust increases. Though  FIG. 4  only shows three IDPs, the model proposed in the Liberty Alliance specification is not so limited. One skilled in the art will readily appreciate that the number of IDPs in a web of trust cannot scale infinitely. Though it is possible to implement a system whereby each IDP can trust every other IDP when there is a small number of IDPs, it is unlikely that such a system can be implemented in a reliable fashion when the number of IDPs scales into the tens of thousands. 
     From the perspective of user  100 , the model presented by the Liberty Alliance has a number of drawbacks. A user&#39;s single sign-on abilities are somewhat restricted. A user is assigned a unique user ID that identifies them to their selected IDP. When a user is authentication by an IDP in the web of trust, the E-tailer is provided a pair-wise unique identifier (PUID) that can be used in the future to identify the user. The PUIDs assigned to two E-tailers for the same user will be different to prevent cross-correlation of user purchases or activities, as the PUID is pair-wise unique. Only the IDP associated with the user holds the PUIDs provided to E-tailers, thus, migration from one IDP to another is not possible. If a user wishes to move from IDP 3   124  to IDP 2   120 , an entirely new identity must be created, and all information stored in IDP 3   124  must be re-entered by the user for storage in IDP 2   120 . This is viewed by many users as handcuffing them to an as yet untested system. As a result, there is great reluctance among many users to register for this service. For E-tailers and potential IDPs, participation in the Liberty Alliance includes agreeing to certain business model restrictions, including how user information must be stored and how it can be used for either statistical or marketing purposes. These restrictions are considered to be limiting the number of parties wishing to participate in the Liberty Alliance. 
     Both Passport™ and the Liberty Alliance provide E-tailers and other sites requiring user authentication with PUIDs. PUIDs allow the e-tailer to store information and build a profile on a user, while preventing two e-tailers from easily correlating their databases to determine user activities and patterns. PUIDs in the liberty alliance are assigned by the IDP holding the user profile, and cannot be matched to the user account by any other IDP, thus if a user chooses to change IDPs all the site specific settings at each E-tailer are lost. This handcuffs users to an IDP providing no more opportunity for portability for most users than the single source Passport™ does. Furthermore, the purpose of the PUID assigned by either Passport™ or the Liberty Alliance can be overcome as earlier discussed by correlating other information such as credit card information. 
     None of the present identity management systems are able to provide both a single sign-on service, specialty information required by many E-tailers, portability of identity information, and as a result none of the services has been able to supplant any of the others. It is, therefore, desirable to provide an identity management system that provides a dynamic user information set, scales and does not rely upon a global data store. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to obviate or mitigate at least one disadvantage of previous identity management systems. 
     In a first aspect of the present invention, there is provided an identity management system for providing authentication of a user to a membersite. The identity management system comprises a root server having a user database for storing a globally unique identifier associated with the user. The root server has means for providing the globally unique identifier to the user, for maintaining a list of network addresses associated with names in a shadow domain for providing to a domain name server, each name associated with either the membersite or a homesite in an identity management network. The root server permits the homesite to authenticate an entity accessing the membersite as the user associated with the globally unique identifier, when the user is redirected to the name associated with the homesite in the shadow domain. The root server may optionally include homesite authenticator for providing the membersite with authentication of the authority of a homesite to authenticate the entity as the user associated with the globally unique identifier. 
     In an embodiment of the first aspect of the present invention, the identity management system includes a homesite, in communication with the root server and having a user profile database, a user authentication engine, and a domain name in the namespace of the shadow domain. The user profile database stores both the globally unique identifier and authentication information associated with the user. The authentication engine allows the homesite to authenticate the identity of the user. The authentication information is optionally a combination of a user ID and password. In another embodiment, the user profile database further stores identity information associated with the user, and the authentication engine includes means to provide the membersite with a subset of the identity information upon authentication of the user. In a further embodiment of the present invention, the authentication engine provides the authenticated user identity to the membersite by providing the user with a cookie containing authentication information readable by the membersite and redirecting the user to the membersite, the cookie is optionally signed by the homesite, and includes indication from the root server that the homesite is authorized to authenticate the globally unique identifier. The indication is optionally an assertion signed by the root server. In another embodiment, the authentication engine provides the identity information associated with the user to the membersite through one of redirection of the user to an authentication encoded universal resource locator, and both providing the user with a cookie containing authentication information readable by the membersite and redirecting the user to the membersite. 
     In a second aspect of the present invention, there is provided a method of providing user authentication to a membersite in an identity management network. The method includes obtaining the name of a homesite, providing the homesite with an authentication request and obtaining the authentication of the user from the homesite. The step of obtaining the homesite name includes obtaining from the user the name of a homesite that can provide user authentication based on user authentication information known to the homesite. The step of providing the homesite with an authentication request includes redirecting the user to the homesite in a shadow domain associated with the identity management network. The step of obtaining the authentication includes obtaining the authentication of the user from the homesite in response to the homesite receiving the known authentication information from the user, the authentication including a globally unique identifier associated with the user. In an embodiment of the second aspect, the step of obtaining the name of the homesite from the user includes the membersite examining a cookie provided by the user. In another embodiment, step of providing the homesite with an authentication request includes the user resolving a name associated with the homesite in the shadow domain to a network address. In a further embodiment the step of providing the homesite with an authentication request includes the membersite providing the user with a cookie, readable by the homesite, containing a request for authentication of the user. In yet another embodiment, the homesite can provide both user authentication information and user identity information, and the step of providing the homesite with an authentication request additionally includes the membersite providing the homesite with an identity information request, while the step of obtaining the authentication additionally includes the obtaining identification information in response to the homesite receiving the known authentication information from the user. In a further embodiment, the method includes the steps of obtaining identity information not provided by the homesite, and providing the obtained identity information to the homesite by redirecting the user to the homesite in the shadow domain, where the identity information not provided by the homesite is obtained from the user. 
     In a third aspect of the present invention, there is provided a method of performing a user authentication at a homesite in an identity management network. The method comprises the steps of receiving from a user, having a globally unique identifier and known authentication information, a request to provide authentication for a membersite; and providing authentication of the user to the membersite in response to receiving known authentication information by redirecting the user to the membersite in a shadow domain associated with the identity management network. In an embodiment of the third aspect, step of the providing the membersite with authentication of the user includes receiving from the user a user ID and password combination associated with the globally unique identifier of the user. In another embodiment, the step of providing the membersite with authentication of the user includes the user resolving a name associated with the membersite in the shadow domain to a network address and further, the step of providing authentication of the user optionally includes the homesite providing the user with a cookie, readable by the membersite, containing authentication of the user and the globally unique identifier associated with the user. In other embodiments, step of receiving a request to provide authentication information includes receiving an identity information request, the step of providing authentication includes the providing the membersite with identification information upon receipt of the known authentication information from the user, and the step of providing the membersite with identification is preceded by obtaining user authorization for the transfer of the requested identification information to the membersite. In another embodiment, the method includes the steps of receiving from the user, identity information obtained by the membersite; and storing the transferred identity information in a user profile database. 
     In another aspect of the present invention, there is provided a method of obtaining a globally unique identifier associated with user having an email address. The method comprises the steps of receiving a request from the user to associate a globally unique identifier with the email address; requesting, from a root server that associates globally unique identifiers with email address, the assignment of a globally unique identifier associated with the user email address; and obtaining the globally unique identifier associated with the email address in response to the user providing the root with a response to a challenge transmitted to the email address. 
     Other aspects and features of the present invention will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments of the invention in conjunction with the accompanying figures. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the present invention will now be described, by way of example only, with reference to the attached Figures, wherein: 
         FIG. 1  is a block diagram of an identity management system of the prior art; 
         FIG. 2  is a block diagram of a identity management system of the prior art; 
         FIG. 3  is a block diagram of a hierarchical identity management system of the prior art; 
         FIG. 4  is a block diagram of a distributed identity management system of the prior art; 
         FIG. 5  is a block diagram of a distributed hierarchical identity management system of the present invention; 
         FIG. 6  is a flowchart illustrating a method of the present invention; 
         FIG. 7  is a flowchart illustrating a method of the present invention; 
         FIG. 8  is a flowchart illustrating a method of the present invention; 
         FIG. 9  is a flowchart illustrating a method of the present invention; and 
         FIG. 10  is a flowchart illustrating a method of the present invention; 
     
    
    
     DETAILED DESCRIPTION 
     Generally, the present invention provides a method and system for identity management. 
     For an identity management system to be successful, users must trust the entity storing their personal information, and must be provided a set of features that encourage the use of the system. Without a sufficient user base the identity management system cannot attract service providers, and is thus unsuccessful. 
     From a user perspective the system must provide a simple registration process with trusted entity. After registration, the user should be provided with a simple method of logging into services using a single login, and should be provided with a simplified mechanism for registering for those services. The user should be provided with a simple mechanism for providing the trusted entity with additional information. Finally, interactions between a vendor/service provider and the trusted entity should be largely transparent to the user. 
     From the perspective of the vendor or service provider, traditional identity management systems have posed problems because of the degree of trust that is required between the vendor and the authentication authority. These trust issues are resolved in the present invention by devolving the trust responsibility to the user. If a user trusts an entity to hold his personal information and serve as an authentication authority, the vendor can be satisfied that the user is comfortable in the trust relationship, and thus the vendor can trust the authentication authority. This trust relationship is sufficient so long as the authentication authority remains in the identity management network. 
     From the perspective of the authentication authority, an agreement made with the user can be designed to serve the business needs of the authority, rather than being dictated by a central body as it is with the Liberty Alliance. Additionally, the authentication mechanism is left to the authentication authority and the user to agree to. Thus, different authentication authorities can employ different authentication mechanisms such as user ID and password combinations, smart cards, biometric samplings and other known user authentication techniques. If a user become disenchanted with either the authentication mechanism or the service provided by the authentication authority, the user can change the authentication authority used to store and authenticate the identity information. 
     To administer the network, a central authority is established. This central authority defines the schema used by the authentication authority for storing the user identity information, which allows the vendors in the identity management network to request information from predefined fields. The central authority also provides a mechanism to both vendors and authentication authorities to ensure that the other party in a communication is a part of the identity management network. 
     All computer systems connected to a public network such as the Internet have an assigned numeric network address. This address serves as a unique identifier and additionally provides routing information so that packets addressed to a network node can be effectively routed to the specified node. To simplify addressing issues for human interactions with the network, alphanumeric domain names are assigned to nodes and a lookup facility is provided, typically through a domain name server (DNS), to allow the alphanumeric domain names to be translated into the numeric addresses. These techniques are well known to those skilled in the art. Another known use of the domain name system is to restrict access to systems within a domain. By only addressing transmissions using the alphanumeric domain name, a transmitting system can restrict systems outside the domain specified in the alphanumeric domain name from receiving the packets. The relative security of the DNS system is trusted by almost the entire Internet to be free from malicious redirection on a global scale. Shadow domains, as referred to in this application, are domains created in the internet under the namespace of a central authority. All entities in the identity management network can be assigned a name in the shadow domain that is resolved to a numeric address associated with the entity. Thus a vendor can have a shadow domain address that resolves to the same numeric address as their primary domain, or it can be resolvable to numeric address different than the primary domain, but associated to another system controlled by the vendor. Technique using shadow domains are preferably used in the present invention to ensure that both a vendor and the authentication authority are in the identity management network. 
     The following discussion will outline the architecture of the identity management network, the roles played by each entity, and will illustrate how the architecture provides for user registration with the identity management network; a single sign on functionality; simplified registration for services requiring user information stored by the authentication authority; a mechanism to update the schema used by the authentication authority to store user data; a mechanism for a vendor or service provider to back-fill user information to the authentication authority; a mechanism for the user to change authentication authorities while maintaining all sign ins and without providing information already stored; and a method for the central authority to remove vendors and authentication authorities from the identity management network. Additionally, security features arising from the architecture and novel trust chains for the signing of certificates and keys will be presented along with other advantages of the architecture and methods of the present invention. 
     In the following discussion, the central authentication authority is referred to as the root of the hierarchical distributed identity management network, or simply as the root. The authentication authority is referred to as a homesite (HS) as it provides a home for the user&#39;s data. Any site requesting either user authentication or user identity information is referred to as a membersite (MS). The user is still referred to as the user. 
       FIG. 5  illustrates an architecture used for the hierarchical distributed identity management system of the present invention. There are four entities in  FIG. 5 , the user  200 , the homesite (HS)  202 , the membersite (MS)  206 , and the root  210 . Each of the entities will be described in relation to the role that they play in the authentication and identity management method. As  FIG. 5  is merely exemplary, additional homesites and membersites are not illustrated, though they may be present. 
     User  200  is a user having a connection to a common public network such as Internet  102 . User  200  has information associated with his or her identity, such as addresses, billing information, and other personal information such as calendar based information. User  200  selects homesite (HS)  202  to store this identity information and to provide identity authentication for single sign on services. 
     HS  202  includes a user profile database (not shown) that is used to store the identity information for user  200 . HS also associates a global identifier (GUID) with the identity information of user  200 . The GUID is a globally unique identifier that is assigned to HS  202  by root  210 , in a method that will be described later. HS  202  has a unique network address, and a domain name  204  associated with the address, here illustrated as homesite.com. Thus to access HS  202 , user  200  can direct a web browser to www.homesite.com, and through a Domain Name Server (DNS) the address will be resolved to the address of HS  202 . 
     Membersite  206  (MS) is a node on the public internet  102  having the domain  208  membersite.com associated with its network address. MS  206  provides a service to which user  200  subscribes, or sells a product that user  200  would like to purchase. To allow user  200  to sign in, or to obtain personal information about user  200 , MS  206  requires either authentication of user  200  or a set of requested information related to user  200 . 
     User  200  provides identity information to homesite  202  (HS). Associated with the information provided by user  200  to HS  202  is a set of identification credentials. For the purposes of the following discussion, the user credentials will be referred to as a user ID and password combination. However, one skilled in the art will readily appreciate that any number of other authentication methods, including biometric readings, static IP traces and smart card derived information, can be used in place of the user ID and password combination. 
     HS  202  has primary domain  206  homesite.com associated with its IP address through the conventional domain name system. HS  202  can be accessed by user  100 , or any other system on the network through both a numeric IP address, and through a domain name associated with that IP address. MS  206  can also be accessed using a unique numeric IP address, or a domain associated with its IP address. In addition to having primary domains in internet  102  (not shown) both HS  202  and MS  206  are connected to each other through a shadow domain administered by Root  210 . Root  210  administers a shadow domain associated with identity management network  212 . Thus, while HS  202  can be accessed by user  200  at its primary domain  204  of homesite.com, and membersite  206  can be accessed by user  200  at its primary domain  208  of membersite.com, they can both be reached in a shadow domain at homesite.com.root.net and membersite.com.root.net respectively. One skilled in the art will appreciate that primary and shadow domain name pairs will both resolve to the same entity, though not necessarily the same address. The shadow domain administered by root  210  is illustrated as identity management network  212 . In the model of  FIG. 5 , identity management and authentication is provided by a distributed hierarchical identity management system. In this system, membersites rely upon any homesite in the same shadow domain to authenticate a user. Whereas previous identity management systems encounter resistance from E-tailers or other service provides because of the amount of trust that must exist between an IDP and an E-tailer, the present model obviates that need. MS  206  relies upon HS  202  only to authenticate that the user  200  has provided the same credentials for authentication that previous users claiming to be user  200  provided. The integrity of HS  202 , the ethics of its business practices, and how it treats the information of user  200  is no longer a concern of the membersite  206  and instead MS  206  relies upon user  200  to determine if HS  202  is trustworthy. If it is determined by a plurality of users that a given homesite in this model is untrustworthy, users will not use the homesite, and can petition for it to be removed from the network by root  210 . Thus, policing of the homesite is a duty assigned to users, not vendors. Additionally, because the network is distributed there is no restriction placed insisting that a membersite cannot also be a homesite. As a result, fear that an IDP will usurp business, and steal customers can be addressed by allowing any membersite to also act as a homesite. The only requirement placed on any membersite or homesite is that they remain part of the shadow domain. 
     To establish an identity profile with HS  202 , user  200  provides profile information and credentials such as a user ID and password, and receives a token indicating that he can be authenticated by HS  202 . In the presently preferred embodiment, the token is a cookie that is referred to as a homesite cookie. This token is accessible to any entity in the shadow domain. When user  200  visits MS  206 , it will present the token only if it is redirected to the shadow domain. To accomplish this, MS  206  can provide a link indicating that all users with identity information stored in identity management network  212  should click to either register or authenticate as the case may be. This link would then redirect the user to the shadow domain  208 , so that the homesite cookies can be retrieved. The user can then be provided a second cookie and directed to HS  202  in either the primary domain  204  or the shadow domain  214 . Alternately, upon visiting MS  206 , user  200  can be redirected to shadow domain  216  and then back to the primary domain  208  so that the cookie is retrieved in advance of a login request. Upon request for authentication through the HS  202 , MS  206  can provide user  200  with the second cookie. The second cookie can be used to request authentication and to provide a challenge to HS  202  that must be signed. This can be used to ensure that HS  202  is in identity management network  212 , and is authorised to authenticate user  200 . These redirections can be done in a manner that is transparent to user  200 . Because user  200  can only provide the cookie to requests to originating the shadow domain corresponding with identity management network  212 , confirmation that HS  202  and MS  206  are in the identity management network  212  is obtained by virtue of the request being completed. A more complete description of how authentications and information transfers are performed is presented below. 
     Root  210  administers the shadow domain to allow verification that HS  202  and MS  206  are affiliated with identity management network  212  by creating shadow domains homesite.com.root.net  214  and membersite.com.root.net  216  for HS  202  and MS  206  respectively. Root  210  also performs a number of other functions including the assigning globally unique identifiers (GUID) to users through interaction with HS  202 ; and defining of an information schema that allows membersites to request information in a standardized manner from a plurality of homesites. Root  210  also provides a mechanism for MS  206  to obtain an encryption certificate from HS  202  and be guaranteed of its authenticity. Root  210  administers the domain root.net, and is thus able to add and remove DNS lookup entries to include or exclude entities from identity management network  212 . In this fashion a shadow domain is administered by root  210  in identity management network  212  to allow membersites and homesites to confirm that the other party in an authentication or information exchange is still in the network. Root  210  also preferably provides HS  202  with a signed assertion to provide a membersite along with authentication of a user, that identifies the homesite authorized to authenticate the user. 
     One skilled in the art will readily appreciate that the elimination of trust relationships between IDPs eliminates many of the scalability issues associated with this model. A single root  210  can administer a domain large enough for a vast plurality of homesites, which allows each membersite in the shadow domain to authenticate user information with each homesite. 
     To understand how the distributed hierarchical structure operates a number of standard operations will now be described. One skilled in the art will appreciate that these methods are merely exemplary and should not be viewed as limiting of the scope of the present invention. 
     As one skilled in the art will appreciate, identity management system  212  preferably identifies each user with a unique identifier. Whereas prior identity management systems have assigned PUIDs, a presently preferred embodiment of the present invention allows a user identity to be globally unique, associated with a single HS, and portable so that it can be moved to another HS. To implement this, each user is assigned a globally unique identifier (GUID) that is assigned by Root  210 , and associated by Root  210  to both a user and a HS. If the user later wishes to change homesites, root  210  can authenticate that request and direct the current HS to forward all information about the user to the new HS. When a user registers with a MS for a service, or to complete a transaction, the GUID is provided to the MS, so that the MS can easily identify the user even after a HS change. In user interactions with the HS, the HS allows a user to associate a user-friendly identifier, much like the user ID of the prior art, with the GUID for ease of identification. Given a set of unique user ID and password combinations, or other user authentication mechanisms, HS  202  can authenticate user  200 , and provide the associated GUID to MS  206  along with a root signed assertion that HS  220  is authorized to authenticate the user. Thus, user  200  interacts with HS  202  using a user friendly userid, but to all other systems in identity management network  212 , user  200  is represented by a GUID. GUIDs are assigned by Root  210 , and it is preferable that they are assigned only when HS  202  is able to provide a valid email address for user  200  that can be verified by root  210 . Verification of the validity of an email address is preferred to ensure that HS  202  does not inappropriately request or create GUIDs for users who are not interested in joining identity management system  212 . 
       FIG. 6  is a flowchart illustrating the steps used in the registration of user  200  in the identity management network. Because each GUID is associated with a homesite and a homesite specific user identifier, it is possible for each homesite to employ its own method of determining a user ID suitable for each user. GUIDs are assigned by root  210  to ensure their uniqueness across the network and to ensure that a homesite is not creating fictitious users in the network. In step  220 , user  200  registers at homesite  202  and requests a homesite specific user ID to which a GUID will be associated. In making this request, user  200  provides homesite  202  with a valid e-mail address. Homesite  202 , prior to obtaining a GUID, communicates the user e-mail address to root  210  and requests that a GUID to be assigned to this user e-mail address in step  222 . Upon receiving the GUID assignment request from homesite  202 , root  210  verifies the validity of the e-mail address in step  224  by sending an authentication challenge to the e-mail address. User  200  receives the authentication challenge in the transmitted email and communicates with both root  210  and homesite  202  in step  226  to prove the validity of the e-mail address. Upon successful receipt of the challenge response, root  210  assigns the e-mail address a GUID, and associates with that GUID both the valid email address and a homesite identifier associated with the homesite that requested the GUID. The GUID is preferably stored by HS  202  in an assertion signed by root  210  that associates HS  202  with the GUID for proof to a MS that HS  202  is authorized to authenticate the GUID. A similar assertion associating the GUID and an email address can also be stored. These assertions are preferably signed and provided with an expiry date to ensure HS  202  does not have the ability to authenticate a user after the user has moved their GUID to another HS In another embodiment. When an entity joins the identity management network  212  as a homesite, the homesite can demonstrate to the satisfaction of root  210  that the email addresses of existing accounts are valid, and without requiring the transmission of a challenge to the email address, root can issue GUIDs for each existing account. This allows a homesite with an existing user base to join the identity management network  212  without having each of its existing users respond to a challenge email. To demonstrate the validity of the email addresses to root  210 , the homesite can provide proof of prior transmissions to the user as evidence of the validity of the email address. 
     Because the trust relationship is between user  200  and HS  202 , it may be desirable for the challenge email to be branded under the identity of HS  202 . To accomplish this, along with the request for a GUID, HS  202  can provide root  210  with an email template for use with the challenge. Thus, the provided template will allow root  210  to send an email that will be branded by HS  202 . The template will allow HS  202  to ensure that user  200  is presented with the challenge email having the logo of HS  202 , and that the challenge email is presented in a language specified by HS  202 . This ensures that the sign in process is seamless to user  200 . 
     In a presently preferred embodiment the step of transmitting a challenge in an e-mail message in step  224  is performed by transmitting a challenge encoded URL to the user. In step  226  the user responds to the challenge by clicking on the URL, and is directed to the destination address. The ability of user  200  to click through a link is considered sufficient proof that a valid user has received the email message. Root  210  will not issue a GUID to HS  202  until it receives confirmation that the user has clicked through. This can be achieved either by having the challenge URL direct user  200  to root  210 , which then redirects user  200  to HS  202  along with a GUID, or the challenge can direct user  200  to HS  202  and provide HS  202  with the challenge response to provide to root  210  on behalf of user  200 . The URL can be directed to HS  202  at either its conventional address or at its shadow domain address to serve as a further guarantee that HS  202  is in the identity management network  212 . 
     In a presently preferred embodiment either the root  210  or the homesite  202 , upon verification of the user  200 , provides user  200  with a cookie that will be accessible to any member of the shadow domain, which constitutes homesites, membersites and root  210 . The placement of the cookies is optional step  228 . This cookie is preferably referred to as the HS cookie and identifies the homesite that should be used to authenticate the user. In a presently preferred embodiment, the homesite cookie provided to the user identifies the homesite by providing an https URL which provides MS  206  with the location that user  200  should be redirected to, and additionally provides MS  206  with the location that the HS certificate can be obtained. In another embodiment the homesite cookie can provide a number of URL&#39;s including one indicating where to redirect the user and one indicating where MS  206  can obtain a certificate from the homesite. Obtaining the HS certificate is important for verification of signatures as is described below. In another preferred embodiment, the cookie both identifies the homesite  202  and includes an assertion by root  210  that the identified homesite is the homesite that can authenticate the user. One skilled in the art will appreciate that MS  206  can obtain information about where to redirect the user from what is referred to as a command URL, while information about where to obtain the HS certificate can be obtained from a certificate URL. Both these URLs can be in the homesite cookie, they can be provided in the DNS system, and the command URL can additionally be provided in the HS certificate. Thus, the homesite cookies may reference a location from which the certificate can be obtained, and in the certificate MS  206  will find the location of HS  202 , or only part of a URL will be in the cookie, and based on the URL fragment, MS  206  will add on known prefixes and suffixes to create both the command and certificate URLs. 
     The above described registration process will now be described from three perspectives, the perspective of the user  200 , the homesite  202  and finally root  210 . From the perspective of user  200 , user  200  visits homesite  202  and requests an identification management account. In making this request, user  200  provides a valid e-mail address and is informed that to complete the process, an e-mail message is being sent to the provided email address. Upon receipt of this e-mail message, user  200  responds to the challenge, preferably by clicking on the URL and thus verifying the validity of the e-mail address. At this point, user  200 , either directly or indirectly, connects to homesite  202  and an identity management account is established. Thus, from the perspective of user  200 , registration for an account is simple process that transparently involves root  210  and thus does not rely upon user  200  trusting root  210  at all. Instead all trust issues are related to user  200  trusting the homesite  202 . From the perspective of homesite  202 , homesite  202  receives a request for a new identity management account from user  200 , this request being accompanied by an e-mail address. The e-mail address is then forwarded to root  210  along with a request for the assignment of a GUID. Homesite  202  then receives the GUID upon successful response to a challenge. In one presently preferred embodiment the response to the challenge is provided to the homesite  202  by the user  200  via the re-direction URL. This challenge response is then transmitted by the homesite  202  to the root  210 , and in response root  210  provides the homesite  202  with a GUID to associate with the user  200 . In an alternate embodiment, the challenge response is provided to the root  210  by the user  200  directly, and the homesite  202  receives a GUID when the user  200  is re-directed to the homesite  202  by the root  210 . One skilled in the art will appreciate that communications between the root  210  and the homesite  202  for the purposes of transmitting the actual GUID are preferably performed in a manner that renders the communication transparent to the user. As will be apparent to one skilled in the art, passing information transparently between root  210  and HS  202  can be achieved using encoded URLs in redirections, redirecting the user with a post based HTTP request, user redirections with cookies as a transfer mechanism, and back channel communications among other known techniques. These same channels can be used for communications between homesites and membersites in later methods. 
     From the perspective of root  210 , root  210  receives a request from the homesite  202  for a new GUID to be associated with the provided e-mail account. To verify that the e-mail account is valid the root  210  transmits to the e-mail account an e-mail message including a challenge. Preferably the challenge is an encoded URL that will be clicked upon by the user  200 . Upon user  200  clicking on the challenge encoded URL, root  210  will receive a challenge response, either from the user  200  or the homesite  202 . Upon receipt of this challenge response, the root will assign a GUID to the e-mail address, and associate it with the homesite  202 . This GUID will be transmitted to the homesite  202 , using known techniques. 
     One skilled in the art will readily appreciate that this process ensures that the root is not assigning GUIDs to a homesite without a valid reason. This maintains the integrity of the identity management system. 
     Another role played by the root  210 , in addition to the assignment of GUIDs, is the definition of a schema which HS  202  will use to store identity data. A defined schema allows MS  206  to request subsets of the user information, and to make any request using predefined field names to ensure a proper response. It should be noted that in a presently preferred embodiment there is no requirement for HS  202  to store the full schema, and in the event that it is asked to provide information about a user that it does not store, HS  202  will either inform user  200  that it does not store the requested information and prompt the user to provide it and then pass the stored and obtained information to MS  206 , or HS  202  will provide MS  206  with the subset of the requested information that is stored, and leave it to MS  206  to prompt user  200  for more information. As a result of not requiring HS  202  to store the full schema for any user, root is able to add new fields to the schema at regular intervals. This allows root  210  to add new fields to store information about new reward programs, or unanticipated requests from membersites. In prior art systems, a schema once defined became static, and the ability to add new fields to the schema was difficult if not impossible. By not forcing a homesite  202  to store the full schema, root  210  can update the schema at any time and rely upon homesites to connect and request the new schema at their convenience. Thus, homesite  202  can check for a new schema at regularly defined intervals, whenever a new GUID is requested, or accompanying any other transaction with root  210 , or using any other schedule defined by homesite  202 . In a presently preferred embodiment the schema is stored as an extensible mark-up language file that can be queried to obtain a variety of information. 
       FIG. 7  illustrates a method by which a homesite  202  is able to obtain an updated schema from the root  210 . In step  230 , the homesite  202  transmits a schema update request to the root  210 . In response to the receipt of the schema update request from the homesite  202 , the root  210  preferably determines the last transmitted schema in step  232 . This preferably entails determining a last transmitted schema date through analysis of the transmitted update request. In step  234 , the root  210  transmits a new schema to the homesite  202  that transmitted the update request. In a presently preferred embodiment, the root  210 , using the determined last transmitted schema, transmits only an updated information list, including the changes to the schema, without transmitting the entire schema. In step  236 , the homesite  202  receives the transmitted new schema information and adopts the new schema elements, and associates unpopulated fields corresponding to each of the new schema elements with each user account. Any of a number of known techniques can be used to populate the new fields, and one skilled in the art will appreciate that the following examples are merely exemplary, and not exhaustive. In one embodiment, upon receiving a new schema, the homesite  202  will e-mail the user to notify them that additional information can be stored in their user profile. In an alternate embodiment, at the time of the user&#39;s next log-in to the homesite  202 , the user will be notified that new schema fields exist and will be prompted to click on a link that will allow the user to populate the new fields. 
     One skilled in the art will appreciate that a number of similar techniques can be used to transmit the new schema to membersites. However, it is likely that membersites will require operator interaction to incorporate requests for new schema held information when a new schema is received. 
     A method of a membersite requesting authentication of a user is described in  FIG. 8 . To provide single sign on abilities to users, the present identity management system preferably employs the homesite cookie provided to user  200  in step  228  of  FIG. 6 . This cookie preferably identifies the homesite associated with the GUID. To ensure that this information is available to all sites in identity management network  212 , the cookie is preferably readable to sites in the domain root.net. Thus, if a membersite attempts to access the cookie, and is not in the shadow domain, the attempt to read the cookie will be rebuffed. However, if membersite  206  is part of the shadow domain, it will obtain a GUID and an indication of the homesite associated with the GUID in step  238 . As described earlier, MS  206  must redirect to the shadow domain to retrieve the cookie. This can either be done with the user clicks a link, or at a previous time. The homesite cookie identifies the homesite that can authenticate user  200 . Upon determining that homesite  202  is identified in the homesite cookie, membersite  206  re-directs the user to homesite  202  with an authentication request in step  240 . To retrieve the authentication request, HS  202  must be in the shadow domain. Thus MS  206  can redirect user  200  to HS  202  in the shadow domain  214 , or in the primary domain  204 . If HS  202  receives user  200  in the primary domain  204 , it will redirect user  200  to the shadow domain  214  so that it can retrieve the authentication request. If homesite  202  is no longer in the shadow domain, the redirection to retrieve the cookie will not be resolved to a valid address, and thus the operation will fail. However, if homesite  202  is in the identity management network  212 , the re-direction request will allow shadow domain address  214  to be resolved to an address that results in user  200  being transferred to homesite  202 . In step  242 , the user provides homesite  202  with authentication credentials. Upon completion of the authentication homesite  202  re-directs the user to membersite  206  either in the shadow domain  216  or in the primary domain  208 , in step  244  and provides membersite  206  with user authentication information that is accessible in shadow domain  216 . Thus depending on the redirection provided by HS  202 , MS  206  may be required to redirect user  200  to the shadow domain  216 . Upon receipt of the authentication and the re-direction of the user, membersite  206  allows user  200  to log-in, in step  246 . In a presently preferred embodiment, the authentication will be signed by HS  202 , and will be accompanied by an assertion signed by root  210  that HS  202  is authorized to authenticate the GUID. 
     One skilled in the art will readily appreciate that communications between homesite  202  and membersite  206  can be effected in any of a number of ways. In a presently preferred embodiment, membersite  206 , upon detection of the homesite cookie, re-directs the user to homesite  202  in the shadow domain as described in step  240  and requests information by providing user  200  with a second cookie to identify the fields in the schema that are required to allow the user to log-in to membersite  206 . Upon receipt of the re-directed user in step  244  and the subsequent authentication, homesite  202  in step  244  will preferably re-direct the authenticated user to membersite  206  in the shadow domain, and provide the authentication information either via the cookie or other known techniques. 
     The above described method will now be described from the perspective of the user, the membersite, the homesite, and finally from the perspective of the root. From the perspective of the user, the user visits a membersite and preferably clicks on a link indicating that they are part of the identity management network. This link re-directs the user to homesite  202  where credentials are presented to verify identity. Upon successful authentication of identity, the user is re-directed back to membersite  206  and allowed in. 
     From the perspective of a membersite, membersite  206  receives an indication from a user that it is registered with a homesite in the identity management network. Membersite  206  then requests and receives the cookie from user  200  in the shadow domain. This cookie identifies homesite  202  as the homesite that can provide authentication. Membersite  206  re-directs user  200  to homesite  202  and requests that homesite  202  authenticate the user  200  and re-direct the user back to membersite  206  after authentication. Membersite  206  then receives the user  200  via a re-direction URL and additionally receives an indication that the user has been authenticated. The indication is preferably accessible in the shadow domain  216 , and is accompanied by a root signed assertion as described above 
     From the perspective of homesite  202 , user  200  establishes a connection as a result of a redirection from membersite  206 . User  200  typically provides a request from membersite  206  to authenticate the identity of the user and re-direct the user upon authentication back to membersite  206 . Typically, this request for authentication and redirection is stored in a cookie provided by the user. Homesite  202  then requests that the user supply credentials to authenticate their identity. Upon receipt of these credentials, and authentication of the identity of user  200  based on the presented credentials, homesite  202  then re-directs the user to membersite  206  and provides membersite  206  with an indication that the user has been authenticated. 
     Root  210  is called upon twice during this process. In both cases, interaction with root  210  is performed to allow the user to be re-directed to a shadow domain name. Thus, when membersite  206  re-directs the user to homesite  202  in the shadow domain, root  210  receives a request for shadow domain name resolution. Upon receipt of this request, root  210  determines the present state of the shadow domain entity. Based on the shadow domain entity&#39;s present state, root  210  resolves the shadow domain name to an address. Thus, if homesite  202  is presently a part of the identity management network, it shadow domain name is resolved to the same IP address that its real domain name would be resolve to. However, if homesite  202  has been removed from the identity management network, resolution of the domain name will result in either an error, or re-direction to a page explaining to the user that homesite  202  is no longer part of the identity management network. Similarly, when homesite  202  re-directs the user to membersite  206 , root  210  receives a shadow domain name resolution request, determines the present state of the shadow domain entity and based on that determined present state resolves the shadow domain name address. 
     One skilled in the art will readily appreciate administration of the shadow domain by root  210  is achieved by maintenance of sub-domains under the root.net domain. Thus, the addition of either a membersite or a homesite to the identity management network entails root  210  modifying a domain name server look-up table to associate an IP address or domain name with a shadow domain name. One skilled in the art will appreciate that due to synchronization of domain name servers on a public network such as the internet, the role of root  210  in resolving the domain names can also be performed by a number of domain name servers that receive data from the root. However, one skilled in the art will appreciate that from a logical level due to the synchronization of domain name servers, all shadow domain resolution requests can be considered to be resolved by root  210 . 
     In addition to providing a single sign on functionality, the present invention provides a mechanism for user  200  to store identification information with HS  202 , and have HS  202  provide the information to MS  206  to facilitate registration for the services offered by MS  206 . This facility appears to user  200  to be a form-filling functionality. 
       FIG. 9  illustrates a method of providing identity information stored by HS  202  to MS  206 . This method allows user  200  to begin a sign up procedure at MS  206 , and have HS  202  fill in the fields in the registration form for which there is a corresponding stored value. Much as with the single-sign on facility provided by the method of  FIG. 8 , the form-filling method of the present invention starts with user  200  indicating to MS  206  that identification information can be provided by a homesite in identity management network  210 . This indication preferably takes the form of clicking on a hypertext link that indicates affiliation with a homesite. After receiving the user notification, MS  206  retrieves the cookie provided by user  200  in the shadow domain  216  and determines a homesite for user  200  in step  248 . User  200  is then redirected to HS  202  along with an information request in step  250 . The information request contains a request for the information needed to fill out fields the form, it does not have to include a request for all the information on the form, and does not need to request all the information stored by HS  202 , thus, MS  206  is able to request a subset of the information stored by HS  202 . HS  202  preferably authenticates user  200  upon receiving the redirection in step  252  to ensure that no one is fraudulently requesting the information of user  200 . Upon authentication, user  200  provides HS  202  with authorization to transfer the requested information to MS  206 . Once again this step is considered optional, through preferred, as it can depend on the terms of service agreed upon between HS  202  and user  200 . HS  202  then redirects user  200  to MS  206 , preferably in the shadow domain to ensure that MS  206  is in the identity management network  212 . Along with the redirection, HS  202  provides MS  206  with the requested information in step  254 . In step  256 , MS  206  receives both user  200  being redirected from HS  202 , and the requested information. If HS  202  has previously authenticated user  200 , HS may not re-authenticate user  200 , and instead will only verify user  200  has been authenticated. 
     One skilled in the art will appreciate that the data stored by HS  202  can be requested by MS  206  in a number of ways. For simply queries, MS  206  can request name and value pairs from HS  202  provided in such a fashion that HS  202  can provide a response in a format that allows MS  206  to receive the information in a desired order. Additionally MS  206  can request information using structured queries to HS  202 . These structured queries are typically replied to using XML based results, though other known techniques of structured replies can also be provided. Queries can also be made to information that HS  202  determines dynamically, or to information that is not directly hosted by HS  202 , and instead is hosted by a third party that HS  202  maintains a link to. For simple queries based on name value pairs, MS  206  can specify the name with which a value is returned so that a value stored in the schema under one name can be returned to a form provided by MS  206  using the form based names used by MS  206 . This allows membersites with pre-existing data collection systems to request information from homesites and receive data via a POST operation to populate the fields in their HTML form. This allows MS  206  to join identity management network with minimal modification to their existing pages. Additionally, in a presently preferred embodiment, the simple query will includes a redirection URL value, so that HS  202  can redirect user  200  to the next page in the data collection phase at MS  206 . To enable the automated form filling, HS  202  will provide MS with the requested information associated with the provided names, optionally in the requested order, and will direct user  200  to the next page in the sign-in procedure by providing a redirection URL that automatically posts the provided data to MS  206 . For structured queries, HS  202  will preferably redirect user  200  to MS  206  with a POST operation that provides the requested structured data, preferably in the form of an XML file. HS  202  may store machine readable data, such as a photo of the user, and can provide it in response to a query from MS  206 . Dynamic data may include such data as a length of time since the last authentication, and can be provided in response to either simple or structured queries. As noted above, HS  202  can store data as a reference to another site, for example, user  200  may have calendar data stored with a third party to which HS  202  stores a link. MS  206  may be an airline that provides a structured query to obtain an XML based report on the availability of user  200  on a given day to schedule a flight. HS  202  can provide either a reference to the calendar site, or can query the calendar site obtain the results and provide them to MS  206 . Communication with third parties, such as a calendar site is preferably achieved using defined protocols. 
     Other data that can be provided in response to queries includes third party assertions that are associated with the GUID. Assertions have previously been discussed in reference to the assertion signed by the root  210  that asserts that a homesite is authorized to authenticate a GUID, but assertions can be provided by other entities as well. Government agencies may provide an assertion associating a birth date with a GUID, so that MS  206  can receive a signed assertion from a trusted authority that user  200  is above a certain age. A mechanism for MS  206  to obtain a certificate or public key with which to authenticate the assertion is discussed below. Other assertions may include indications that users have achieved a premium service level with a reward program. This assertion could be used by a membersite to provide user  200  with a discount for a service based on the premium reward membership. Other assertions, signed by third parties, will be apparent to those skilled in the art. Assertions can either be stored by HS  202 , or they can be stored as links by HS  202 , to allow MS  206  to retrieve the assertion directly from the third party. 
     Whereas simple queries are commonly responded to through URL encoding, extensible queries are preferably responded to by passing information to MS  206  through a HTTP post operation. 
     Because the schema used to store user information is dynamic, a mechanism for acquiring user information after an initial sign up is required. While it is envisaged that HS  202  can prompt user  200  to add information during an authentication or information request, the present invention provides a novel method of obtaining user information for storage by HS  202 . This method is illustrated in the flowchart of  FIG. 10 . 
     The present architecture allows the user to populate schema fields or modify existing information stored by the homesite  202  from participating membersites  206 . This method is illustrated in  FIG. 10 . Upon requesting and receiving information about the user from the homesite  202 , the membersite  206  determines in step  258  that it requires more information, and thus prompts the user  200  to enter this information, in an alternate embodiment, MS  206  asks the user to confirm the information provided by HS  202 . In step  250  the user provides this information to the membersite  206  and indicates, preferably by clicking on a hypertext link, that this information should be transmitted back to the homesite  202 . At this point, the membersite  206  re-directs the user to the homesite  202  using the shadow domain address and transfers to the homesite  202  the information provided by the user. The transfer of information provided by the user can take place using back channel communication, an encoded URL in the form of a simple query, or in cookies carried by the user. After receipt of both the re-directed user, and the transmitted information, the homesite  202  presents the user with the information, and asks for approval of the information. Upon receipt of the approval of the information from the user  200  in step  254 , the homesite  202  stores the information in the schema. At this point, the user is re-directed back to the membersite  206  in step  256 . In another embodiment, MS  206  determines that as a result of its interaction with user  200  that new information is available that should be provided to HS  202 . MS  206  then requests user authorization to transfer the data back to HS  202 , as in step  260 , and the process continues as described above. As an example of the alternate embodiment, MS  206  is an airline that has booked a flight for user  200 . MS  206  has structured information that should be provided to HS  202  to store in the calendar of user  200 . The structured data is preferably transferred as an XML file containing the flight number, destination, takeoff and landing times and other related information. HS  202  can respond to the update by either storing the data if it hosts the calendar for user  200 , by redirecting the information to the calendar provider if it is a third party, or by providing MS  206  with an address to which the information should be sent. Thus the information provided to HS  202  can be structured or simple, and it can be either stored or referenced data. In a presently preferred embodiment, MS  206  does not require user authorization for all updates of HS  202  information. In the above example of an airline booking, if the flight is delayed, MS  206  can preferably automatically update HS  202  without requiring user approval. 
     As noted earlier, one of the benefits of the present invention is that the information stored by a homesite is portable to another homesite. There can be any of a myriad number of reasons that a user would want to move their data from one homesite to another, including cost, the amount of information a homesite is willing to store, and the terms of service the homesite operates under. Whereas in prior art systems there was either no equivalent to transfer data to, or the data was non portable, the present system ensures the portability of user data by assigning user  200  a unique GUID and requiring that HS  202  stores user information in a defined schema. Thus, to change a homesite, user  200  visits a second homesite and indicates requests a new account to be associated with an existing GUID. By maintaining the same GUID, a user will be able to maintain any accounts membersites that have stored information using the GUID as an identifier. Much as with the registration process, root  210  issues a challenge to user  200 , requiring the user to respond to the challenge to ensure that a misbehaving homesite is not attempting to steal users from another. The transfer of registration process is identical in the challenge response phase, and upon successful completion of the challenge response, root  210  issues a directive to the existing homesite to transfer all schema related information to the new homesite. This can be accomplished either using back-channel communications, URL encoding, or preferably by root  210  redirecting user  200  to the original homesite, having the original homesite provide user  200  with a cookie containing all stored personal information, and then redirect user  200  to the new homesite. The redirection from the first homesite to the second homesite can be accomplished by redirecting the user  200  to root  210  so that the original homesite does not know where the user has gone to. Upon being, either directly or indirectly, redirected to the new homesite, user  200  provides the cookie that stores all the schema related information, and receives a new cookie confirming the GUID, and indicating that the new homesite is the site to be associated with the GUID 
     In a presently preferred embodiment, to obviate the need to retransmit challenge emails, the newly selected homesite can direct the user to the initial homesite for authentication. Successful completion of this authentication can be considered by root  210  as proof that the user has the authority to transfer the GUID to another homesite. 
     Whereas prior art methods of identity management provided membersites with PUIDs, the present invention provides GUIDs that due to their global nature can be used to obtain third party assertions. PUIDs cannot support third party assertions without the IDP sharing the PUID mapping with a third party, thus negating the purpose of a PUID. To provide user  200  with the advantages offered by PUIDs, HS  202  can allow a user to obtain multiple GUIDs. By obtaining multiple GUIDs, user  200  can create a plurality of online personas so that different membersites cannot correlate behaviour online. This provides user  200  with the option of obtaining the security of PUIDs, while still retaining the benefits of GUIDs. To allow the management of multiple GUIDs, user  200  will be prompted by HS  202  upon authentication as to which GUID should be provided to a membersite. This allows a user to provide HS  202  with one set of information, and have different profiles set up for each GUID. Thus a work based persona with a GUID can default to providing an office phone number and address when a membersite requires a phone number and address, while a home based persona with a different GUID can default to providing a home phone number and address when requested. 
     As discussed above, assertions are preferably provided by root  210  to provide proof to a membersite that HS  202  is authorized to authenticate a GUID. Preferably this assertion is signed using a private key or certificate, and the signature can be verified using a public key or certificate. The certificate is preferably obtainable through contact with root  210  over a secure data channel. To ensure that the certificate has not been tampered with, the certificate of root  210  is preferably signed by a first certificate authority (CA), and transmitted to a requesting party over an SSL link that is signed by a second distinct CA. This double chain of signatures requires that both the first and the second CA be compromised for a malicious party to be able to impersonate root  210 . The authentication information provided by a homesite is preferably signed by the homesite, so that it too is a credential. This information is preferably signed by the homesite, so that the membersite can be sure that it has not been tampered with, or that the homesite is being impersonated by a third party. To verify assertions made by the homesite, a membersite can obtain a certificate from the homesite over an SSL connection signed by a CA, with the homesite certificate signed by the root. Because the CA and the root are distinct, there is another double chain for security, requiring a breach of security at both the CA and the root. Third party assertions are preferably signed, with a certificate available over an SSL connection, the certificate signed by root or a CA, and the connection signed by a CA distinct from the one that may have signed the certificate. The above double signature transmission is preferred for the verification of certificates transmitted in identity network  212 . 
     In a presently preferred embodiment, when presented with a signed assertion, MS  206  will obtain the certificate used to verify the signature and cache the certificate. In the next signature verification that uses that certificate, MS  206  does not have to re-request the certificate, but must be sure that the certificate is up to date. To do this, MS  206  performs a DNS txt lookup on the shadow domain name of the certificate holder. Root  210  in providing DNS services for the shadow domain maintains in each entity&#39;s txt DNS field their certificate number. If the value returned from the DNS lookup is identical to the certificate number, MS  206  can verify the signature, if the certificate number is different, MS  206  then discards the cached certificate and requests a new certificate. 
     To allow a membersite to enter identity management network  212  without adding in scripting functionality that allows key management, and shadow domain shifting, it is possible for MS  206  to have its shadow domain  216  associated with a third party that processes the reading of the homesite cookie, the redirection to HS  202  and the provision of the data provided by HS  202 . Additionally, this third part can handle the signature checks required to verify the integrity of the received data. One skilled in the art will appreciate that this functionality can be provided by a single entity for numerous membersites. 
     One common request for existing single sign in services is the provision of a single sign out facility. To provide this, a membersite that has allowed a user to sign in, preferably modifies a cookie carried by user  200 . This cookie tracks the membersites to which a user is logged in. In a presently preferred embodiment, the cookie provides a URL that will allow a user to log out. To sign out of services, user  200  returns to his homesite  202  and indicates that he wishes to log out of all services, or a subset thereof. The homesite  202  can then work through the URL&#39;s provided in the cookies to allow the user to have a single click sign off. Alternately, MS  206  can provide a logout link to user  200  that can either log user  200  out of MS  206 , and remove the membersite reference in the cookie, or redirect user  200  to HS  202  so that the logout process described about can be pursued. In another embodiment, when HS  202  authenticates user  200  for MS  206 , HS  202  can store in the user profile database a logout URL for MS  206 . Thus, to log out, user  200  would visit HS  202  and request a list of sites at which a login is current, this list would also preferably provide the user with the ability to logout of any or all membersites. 
     The present invention provides users with simplified sign in and registration with membersites, allowing the user to visit a membersite, and indicate that they are part of the identity management network. This is preferably done by clicking on either an icon or a link on the sign in page. When this link has been clicked upon, MS  206  will retrieve the cookie identifying user  200 , and will redirect user  200  to HS  202 . In the case of simply signing in to MS  206 , where a previous registration has been made the redirection to HS  202  is simply for authentication. If user  200  has not previously registered with MS  206 , the redirection to HS  202  is for both authentication and for an information request. MS  206  can request a subset of the information stored at HS  202 , using either a simple URL encoded redirection, or can request extensible information through the use of a query stored in a cookie carried by user  200 . The redirection of user  200  to HS  202  sends user  200  to the shadow domain of HS  202 , to ensure that HS  202  is still in the identity management network. After providing HS  202  with authentication credentials, and any required authorization for data transfer, user  200  is redirected to MS  206 . The checks to ensure that both MS  206  and HS  202  are in the shadow domain, and thus are active in the identity management system are performed transparently to the user, and allow the user a simplified process for login and registration. Through the ability of MS  206  to pass information back to HS  202 , user  200  is provided with a simplified mechanism for ensuring that HS  202  has updated and new information. 
     Because user  200  authenticates at HS  202  after a redirection from MS  206 , user  200  is typically requires to verify that a correct redirection has been made by checking the URL which is typically in a navigation or location bar in the browser window. To provide additional security, HS  202  can store a series of user preferences, obtained from user  200 , that define a user interface and experience. These preferences may include a user defined background page colour, a customized set of icons, a user defined greeting and a user selected language interface. These preferences can be obtained from user  200  at the time of registration, stored in the user profile database, and retrieved when user  200  is redirected for authentication. If a malicious party attempts to impersonate HS  202 , the user defined preferences will be unavailable, and as a result, user  200  will be immediately aware that they have been redirected to the wrong site. 
     The hierarchical structure of the present invention provides a single point from which security breaches can be addressed, while the distributed nature of the homesites eliminates the single point of failure that releases user information. If the integrity of root  210  is compromised, removal of all root.net domains can be easily achieved by contacting DNS authorities, which will shut down the entire identity management network  212 . This will prevent the release of any user information, and will prevent fictitious homesites from allowing user impersonation. If root  210  is comprised, there is no user specific data released as opposed to the Passport™ model. If a single homesite is compromised, its user data is released, but by removing it from the shadow domain, it is prevented from providing improper authentications, as it will be unable to retrieve cookies from the shadow domain. Thus, a compromised homesite can be effectively removed from the network in the time it takes an address update to be propagated through the DNS network. In the Liberty Alliance model, which provides no single point of failure, due to the complex key ring in the web of trust, there is no simple method of removing a compromised IDP from the web. Thus, the present invention, through its structure eliminates a single point of failure that will allow the release of user data, and provides a mechanism for isolating compromised homesites to prevent impersonations of users. 
     The above-described embodiments of the present invention are intended to be examples only. Alterations, modifications and variations may be effected to the particular embodiments by those of skill in the art without departing from the scope of the invention, which is defined solely by the claims appended hereto.