Abstract:
Embodiments of the present invention relate to methods and apparatus for sharing information with third parties and providing mechanisms whereby those third parties may legitimately pass the personal information on to other, for example affiliated, third parties. In one example of information sharing, information is shared electronically between an information provider and an information requester, the information provider storing a body of information and associated sharing criteria provided by an originator, receiving a first information request from a first requestor and revealing the information and the sharing criteria to the first requestor if the first request is authorised by the originator, receiving a second information request from a second requestor and revealing the information to the second requestor if the second request contains an information identifier obtained from the first requester and the sharing criteria so permits, and storing evidence of information requests.

Description:
[0001]    People in general would like to restrict or control who has access to their personal identifying information, such as name, age, marital status, address, telephone number, national insurance number and the like. This is particularly true when individuals are required to share information with organisations who need to know the information in order to be able to fulfil obligations to the individual, e.g. to deliver a service. Individuals have to trust that the organisations will respect their privacy. However, there are regular reports in the press describing instances where personal information has been lost, misplaced or misused, and individuals end up with a distinct lack of faith—or trust—in organisations that request personal information. Part of this mistrust arises from reported privacy breaches, but it is also fuelled by a perceived lack of clarity and understanding about how personal information is used and by a fear that it will in any event be misused. 
         [0002]    While the only way to guarantee that personal identifying information will not be lost, misplaced of misused is to not disclose it, this would be impractical in many if not most scenarios. However, systems and methods that enable individuals to maintain increased control over how their personal identifying information is used are desirable. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0003]    Embodiments of the invention will now be described, by way of non-limiting example, with reference to the accompanying diagrammatic drawings, in which: 
           [0004]      FIG. 1  is a schematic diagram that shows an example of a three corner architecture including a user, an information provider and a relying party; 
           [0005]      FIG. 2  is a schematic diagram that shows an example of a four corner architecture including a user, an information provider, a first relying party and second relying party; 
           [0006]      FIG. 3  is a diagram that shows an example of a four corner architecture including a user, an information provider, a first relying party, second relying party and a cascade of additional relying parties; 
           [0007]      FIG. 4  is a schematic diagram that illustrates how the additional relying parties can be modelled as second relying parties according to embodiments of the present invention; 
           [0008]      FIG. 5  is a schematic diagram that illustrates an exemplary computer user interface presented by an on-line information provider for a user to enter their personal information and associated deletion and sharing preferences; 
           [0009]      FIG. 6  is a flow diagram illustrating a protocol for passing user information from an information provider to a first relying party on the basis of user sharing preferences; 
           [0010]      FIG. 7  is a flow diagram illustrating a protocol for revealing user information to a second relying party on the basis of a general proof token acquired automatically by a first relying party from a respective information provider; and 
           [0011]      FIG. 8  is a flow diagram illustrating a protocol for revealing user information to a second relying party on the basis of a specific proof token acquired in response to a request by a first relying party from a respective information provider. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0012]    By way of background, two known models for identity sharing employ federated and centralised architectures. The approach referred to as federated identity management is characterised by the need to securely identify and authenticate individuals across multiple domains, and essentially embodies the concept of decentralised single sign-on. By contrast, centralised identity management is where individuals operate within the same ‘domain of control’, usually within the same organisation or network. This centralised approach is seen in wide use today, particularly with internal ‘corporate’ implementations and eCommerce solutions. However, individuals are generally not concerned whether the architecture they use is federated or centralised. They are simply concerned about the use of the personal information that they share with an organisation. 
         [0013]    Although at least some of the examples that follow are based on a federated architecture, it will be appreciated that embodiments of aspects of the present invention may be applied to either federated or centralised architectures. 
         [0014]    The diagram in  FIG. 1  illustrates a federated architecture, in which a user  100  trusts third party information provider  110  with their information. A third party  120 , which is, for example, an organisation that requires a user&#39;s information for some legitimate reason, is able to interact with the information provider  110 , given the user&#39;s permission, in order to obtain the user&#39;s information. The premise of the architecture in  FIG. 1  is that both the user  100  and the third party  120  trust the information provider  110 . The user  100  trusts that the information provider  110  will not lose, misuse or misplace the information, and, moreover, will not disclose or reveal the information other than to parties authorised by the user. The third party  120  trusts the information provider  110  to ensure that the user&#39;s information is genuine. For this, it is expected that the information provider  110  would have authenticated the information it received from the user  100 . 
         [0015]    Although not shown in  FIG. 1 , the interactions between the user  100 , the information provider  110  and relying party  120  would typically be by respective computers, for example operating under a HPUX™, Linux™ or Windows™ operating system, connected by standard arrangements of networks such as the Internet, or intranets, either directly or via access networks (which can be either by physical or wireless connection). Of course, individual communications across networks between entities would typically be protected by known security and privacy encryption protocols, for example SSL. 
         [0016]    The diagram in  FIG. 1  illustrates an example of a so-called ‘three-corner model’, due to the three players that are involved. The model is useful in the sense that the user  100  is fully aware of the information that is released by the information provider  110  to a third party  120 , which will be referred to as a ‘relying party’, in the sense that the party is reliant upon the information for some reason. However, the model does not cater for situations in which the relying party  120  wishes to pass the information it received to another relying party (not shown), for example a partner organisation. If the relying party is entirely trustworthy, it may simply not pass information to other entities, assuming that is what the user wishes. If the relying party is not entirely trustworthy, it uses imperfect procedures to protect user information, or it relies on tacit user approval if they have not specifically disallowed information from being passed in this way, it is most likely that neither the user  100  nor the information provider  110  would know of any information transfer by the relying party  120  to another relying party (not shown). 
         [0017]    While the diagram in  FIG. 1  illustrates communications between the relying party  120  and the information provider  110  (via path a) in order to obtain the personal information, this may not be necessary. For example, the information provider  110  may at the request of the user pass information that is required by the relying party  120  back to the user  100  (via path b). The information may be passed back in verifiable form, for example signed by a private cryptographic key of the information provider  110 . Then, the user  100  may pass the information to the relying party  120  (via path c), which can verify the validity of the information using a respective public key of the information provider in a known way. 
         [0018]    It will be appreciated that direct communications between the information provider  110  and the relying party  120 , via path a, or indirect communications between the information provider  110  and the relying party  120 , via paths b and c, are alternative but equally valid options that would find application (unless otherwise stated or the context dictates otherwise) in the scenario in  FIG. 1  and in the various scenarios that follow. 
         [0019]    The diagram in  FIG. 2  illustrates an architecture according to exemplary embodiments of the present invention, which can be referred to as a ‘four corner model’. The four corners are inhabited by a user  200 , an information provider  210 , a first relying party  220  and a second relying party  230 . The model is conceived to accommodate situations in which the first relying party  220  wishes to pass information it received from the information provider  210  to the second relying party  230 , in a way which keeps the user fully informed of such information passing. 
         [0020]    As with the example in  FIG. 1 , the information may be provided to the first relying party  220  either directly by the information provider  210  or indirectly through the user  200 . 
         [0021]    The four corner model can be extended as illustrated by the diagram in  FIG. 3 , in which there is user  300 , an information provider  310 , a first relying party  320 , a second relying party  330  and a cascade of additional relying parties, each receiving information from a previous relying party. Although the cascade in  FIG. 3  appears more complex than the simple four corner model in  FIG. 2 , for the present purposes, it is apparent that third  340 , fourth  350 , fifth  360  (and so on up to  390 ) relying parties are each equivalent in terms of status to the second relying party  330 . This can be illustrated as shown in  FIG. 4 , wherein each subsequent relying party ( 440 - 460 ), which receives information, appears to be the equivalent of a second relying party  430 , if the four corner model is applied. 
         [0022]    The diagram in  FIG. 4  includes a user  400 , an information provider  410 , a first relying party  420 , and second  430  to fifth  460  subsequent relying parties. In essence, the third, fourth and fifth relying parties each appear to be the same distance, in terms of ‘hops’ between players, from the user as the second relying party  420 . In  FIG. 4 , the players are shown to obtain information directly from the information provider  410 , via paths a, a′, a″ etc, and so the number of hops is one (that is, from the information provider directly to the relying party). If the information goes via the user  400 , which is not illustrated in  FIG. 4 , the information could be provided directly by the user to the respective relying party, and then the number of hops would be two (that is, from the information provider to the user and then to the respective relying party). Alternatively, if the user and information provider are treated as being the same logical entity (as they trust one another), then all relying parties can be thought of as being just one hop away from the user/information provider. In any event, according to the model in  FIG. 4 , each (subsequent) relying party can be thought of as a ‘first’ relying party. However, for ease of understanding only, relying parties will continue to be referred to as first, second, subsequent, etc. 
         [0023]    Therefore, it is sufficient for the present purposes to consider only the simple four corner model of  FIG. 2 , although it is clear that what follows may be applied to any degree of cascaded relying parties. 
         [0024]    As will be described, through an information provider, users can monitor and guide actions of organisations with which they share information, and, according to embodiments of the invention, can subsequently collect evidence of authorised and possibly unauthorised sharing (or attempted sharing). Such evidence enables the user to make informed choices about whether to trust an organisation in future. As described, according to embodiments of the invention, information may be thought of as being just ‘one hop away’ from the user irrespective of the number of shares by one relying party to another. The model provides a framework in which it appears the user has authorised information to be shared with each organisation directly, for example, as illustrated in the diagram in  FIG. 4 . 
         [0025]    An embodiment of the present invention will now be described with reference to the four corner model illustrated in  FIG. 2 , in which the information provider  210  acts as an identity provider (IDP), which stores personal identifying information (P 11 ). The PII is provided by users who trust the IDP  210  to look after their information. PII may include, for example, full name, age, marital status, sex, address, telephone number(s), national insurance number, social security number, health insurance number and the like. In addition to the PII, users provide sharing criteria, in the form of personal sharing preferences (PSP). The PSP inform recipients of the PII how, and indeed whether, the information can be shared by the recipients with other third parties. The preferences, of course, are adhered to by the IDP, as it is trustworthy, and should be adhered to by the recipients. As will be described, the preferences may include other criteria, such as ‘delete’ criteria. 
         [0026]    PSP are typically set by a user  200  via an on-line user interface  500 , for example as illustrated in the diagram in  FIG. 5 . The user interface  500  may be provided as part of an on-line sign up software application, which is typically provided by the IDP  210 . In  FIG. 5 , a user  200  is given an opportunity to identify various items of PII, for example, name  501 , address  502 , e-mail address  503 , telephone  504 , etc., in respective form fields in a left hand column  510  of the interface  500 . Associated with each item of PII is a ‘Delete Preference’ in a middle column  520 , and a ‘Share Preference’ in a right hand column  530  of the interface  500 . 
         [0027]    The Delete Preference for each item of PII include: ‘Delete After Transaction’, ‘Delete in 30 Days’, ‘Delete in 6 Months’ and ‘Keep Forever’. The Delete Preferences, in effect, provide the user with an opportunity to specify a shelf-life of the associated item of PII, after which time it is deemed out of date or no longer valid. The user would need to provide replacement data if any Delete Preference other than ‘Keep Forever’ is selected. In the example provided in  FIG. 5 , all data shown is likely to remain the same and, accordingly, ‘Keep Forever’ is appropriately shown selected. 
         [0028]    The Share Preferences for each item of PII include: ‘Don&#39;t Share’, ‘Share With Marketing’, ‘Share With Carefully Selected Partners’ and ‘Don&#39;t Share’. The Share Preferences, in effect, provide the user with relatively granular control over whether the information can be shared and with whom it may be shared. Don&#39;t Share is self explanatory and it may apply to everyone except the user. This option may be used, for example, with a private encryption key belonging to the user. In effect, the IDP  210  becomes a secure repository for sensitive information. Share With Marketing indicates that the information can be shared with related companies of relying parties, for the purposes of gathering marketing information only. Relevant marketing information may be post (or zip) code information, indicating where users (who may be customers) live. It would not be appropriate to share this kind of information in a way which enables third parties to make contact with the user. Share with Carefully Selected Partners indicates that a relying party may share the information with others who may wish to contact the user, for example to sell goods or services that are in some way related to products or services brought by the user from the relying party. Share With All is self-explanatory. 
         [0029]    The ‘Share’ and ‘Delete’ preferences are just two examples of the control that a user might want to impose on his PII. In practice, there could be many more types of preference, and some could be quite sophisticated, requiring other conditions external to the transaction to be met first. For example, a user might say, “Delete my data and never contact me again.” Of course, to achieve this, a relying party would have to keep at least an element of PII in order to record not to contact the user. As such, there would need to be logic that informs the user that the preference comprises mutually exclusive demands, one of which would need to be compromised on. 
         [0030]    It will also be appreciated that PII can be defined in many other ways. For example, instead of having one set of PII in which each item has associated deletion and sharing preferences, there may be plural sets of PII for each user, with each set having single associated deletion and sharing preferences. In this way, a set having no sensitive information may have liberal PSP, for example permitting the information to be shared with anyone. Sets comprising additional, and/or more sensitive information would have more restrictive associated PSP. 
         [0031]    An exemplary process for revealing PII to a first relying party  220 , will now be described with reference to the flow diagram in  FIG. 6 . The flow diagram includes three participants; a user  600 , a first relying party (RPa)  620  and an IDP  610 . In a first step [ 625 ], the user  600  signs up with the IDP  610 . In this procedure, the user  600  provides the PII and the IDP  610  authenticates the information in a known secure way. In addition, the user  600  assigns PSP to the PII, so that the IDP  610  knows how to treat the information. Next [ 630 ], the user  600 , for example, applies for an on-line service or initiates the process for buying a product. In response to the application, the relying party RPa  620  (for example, an on-line service provider or seller) requests PII from the user  600  [ 635 ]. The user  600 , in turn [ 640 ], contacts the IDP  610  and requests a token. The token may be a reference to the PII or it may be the PII in encrypted form and it identifies the originating IDP  610 . The IDP  610  authenticates the user  600  and provides the token [ 645 ]. In a next step [ 650 ], the user  601  delivers the token to the relying party RPa  620 . The RPa  620  receives the token, identifies the IDP  610  and determines whether or not it can trust the IDP [ 655 ]. For example, the RPa may only trust a pre-determined set of selected identity providers. If the IDP is trusted by the RPa  620 , then the RPa sends a request for the PII, including the token, to the IDP  610  [ 660 ]. The IDP  610  authenticates the token and checks the request against the associated PSP, to ensure that the requested PII can be revealed to the RPa  620  [ 665 ]. Assuming the token is verified and the request is allowed, the IDP  610 , reveals the PII and the associated PSP to the RPa [ 670 ]. If the token is a reference, the act of revealing involves sending the PII to the RPa. If the token contains an encrypted version of the PII, the act of revealing may involve providing a key for the RPa  620  to decrypt the PII that it has already received from the user  600 . Next [ 675 ], according to the present embodiment, the IDP  610  stores evidence of the request (irrespective of whether or not the request is completed by the IDP). Next [ 680 ], the RPa  620  determines whether or not the PII is suitable for the required purpose. Assuming it is, finally, the RPa  620  delivers the service or product to the user [ 685 ]. Service delivery may involve an actual delivery of some kind or it may simply permit the user to be authorised to access a web service or the like. 
         [0032]    The flow diagram in  FIG. 6  illustrates one way of delivering information and associated personal sharing preferences to a relying party in which the relying party obtains the information directly from the identity provider. As has already been mentioned, an alternative would be for the relying party to receive the information and personal sharing preferences from the identity provider via the user, the information having been verified by the identity provider. 
         [0033]    An exemplary process involving an IDP  610  for passing PII from a first relying party RPa  620  to a second relying party RPb  730  (which can be thought of as also being a first relying party according to embodiments of the present invention) will now be described with reference to the flow diagram in  FIG. 7 . It is assumed that the RPa has already obtained the PII and associated PSP, for example by the process of  FIG. 6 . 
         [0034]    According to  FIG. 7 , in a first step [ 735 ], the IDP  610  generates a message M 1  (or messages) to pass the PII and associated PSP to the RPa  620  along with a general proof token T. In the present example, T takes the general form {TokenRef, I RPn }E IDP , where TokenRef is a unique identifier (e.g. an alphanumeric string) generated by an IDP, I RPn  is the identity of an intended relying party n and { . . . } E IDP  indicates that the information within the braces is encrypted by IDP&#39;s private encryption key E IDP . In this way, it can be seen that T binds an originating relying party, in the present instance RPa, to the TokenRef in a way that can only be revealed by the IDP  610 . As will be described, the IDP will know that any request for PII it receives containing T is a legitimate request for information obtained via RPa. In other words, the general proof token is bound to RPa for all future uses of the token. 
         [0035]    Returning to  FIG. 7 , the information {PII, PSP, T}, where T includes I RPa , is signed by a signing key S IDP  of the IDP  610  so that the RPa  620  has an assurance that the information is genuinely from the IDP  610  and can be trusted. For security purposes, the signed information is also encrypted using a public encryption key S RPa  of RPa  620 . Accordingly, only RPa, which has a respective private decryption key P RPa , is able to decrypt the information. This step [ 735 ] is analogous to step  670  in  FIG. 6 , in which the PII is revealed to the RPa. However, in  FIG. 7 , T is also passed to the RPa, to enable the RPa to initiate the process of passing PII to the RPb  730 , as will now be described. 
         [0036]    In a next step [ 740 ], the RPa wishes to pass the PII to a third party, the RPb. However, the RP a  is trustworthy and so it is arranged to evaluate the PSP to determine whether any PII can be shared and with whom. According to the present example it is assumed that PII can be shared with RPb. 
         [0037]    Next [ 745 ], the RPa  620  generates a message M 2  to pass to RPb. M 2  includes T and an identifier I RPb  (identifying RPb) both signed by the signing key S RPa  of the RPa so that any recipient can establish that the information originated from RPa. This signed information is then encrypted using the public encryption key E IDP  of IDP  610 . In effect, RPa augments T by binding it also to the identity of RPb. In other words, T is now bound both to RPa  620  and to RPb  730 . The augmented proof token {{T, I RPb } S RPa } E IDP  is accompanied by an indication A, specifying which elements of the PII RPa is willing to reveal to RPb, and the identity I of the IDP (including, if necessary, information on how to connect to and communicate with the IDP). As a security measure, the entire message is then encrypted using the public encryption key E RPb  of RPb, so that only RPb can extract the information. With respect to A, in some instances, RPa may be willing to reveal all of the PII, in other instances, in particular if the PSP dictates that only a subset of the PII can be revealed, the set of information available to RPb may be restricted to fewer specified information fields: and A may or may not be necessary. 
         [0038]    Next [ 750 ], the RPb  730  receives M 2  from RPa  620  and undertakes to obtain the information from the IDP  610 . RPb generates a request message M 3  including the augmented proof token {{T, I RPb } S RPa } E IDP  and an indication R of which information it requires. R is most likely to be the same as, or a subset of, A, depending on RPb&#39;s requirements. The augmented proof token and R are signed using a signing key S RPb  of RPb and, for security, encrypted using the public encryption key E IDP  of IDP  610 , so that only the IDP  610  can extract the information. 
         [0039]    In a next step [ 750 ], on receipt of message M 3 , the IDP  610  extracts and identifies TokenRef and its binding with RPa  620 . In addition, the IDP  610  identifies the new binding between T and RPb  730 , which is a new player in the process as far as the IDP is concerned. However, the IDP  610  can see that the request is legitimate as it has originated from RPa  620 , and RPa had clearly intended RPb  730  to be able to request the information, as RPa had bound RPb&#39;s identity to T, signed the augmented proof token and encrypted it as evidence for the IDP  610 . 
         [0040]    Next [ 755 ], the IDP  610  evaluates R and compares it with the PSP that are associated with the PII. Assuming R complies with the PSP, the IDP  610  generates a final message M 4  to send to the RPb  730 . M 4  contains PII′ (or a subset thereof indicated by R), PSP′ (in case the RPb wishes to enable a subsequent relying party to obtain any PII) and a general proof token T′, all signed by IDP&#39;s signing key S IDP  and encrypted, for reasons of security, by RPb&#39;s public encryption key E RPb . In this case, T′ is similar to T except it is bounds to RPb by the inclusion of I RPb  instead of I RPa . As explained, PII′ may be the same as PII or it may be a subset of PII. Additionally, or alternatively, PII′ may contain updated information, which has changed or been refreshed since the original information was made available to RPa. Indeed, if the PSP has been modified (in which case it is PSP′), the PII′ may be restricted in some other way than was originally intended. 
         [0041]    In essence, step  760  is analogous to step  735  and, if PSP′ permits, the RPb  730  may initiate another cycle of the process by passing a message comparable to M 2  to another relying party. 
         [0042]    Finally [ 765 ], the IDP  610  generates evidence that the information has been sent to RPb. In the event the PSP does not permit the PII to be sent to RPb, the IDP  610  still generates evidence of the request, which can be traced back to RPa. Subsequently, the user may review the evidence and decide that he no longer trusts RPa  620 , which would influence how (or whether) he interacts with RPa in future. 
         [0043]    It will be apparent that the process illustrated in  FIG. 7  permits a first relying party to forward a general proof token directly to a second or subsequent relying party without recourse to a respective identity provider. In this case, the RPa is trusted to bind the proof token to the identity of the second or subsequent relying party. 
         [0044]    An alternative process for passing information to a second or subsequent relying party will now be described with reference to the flow diagram in  FIG. 8 . 
         [0045]    According to  FIG. 8 , in a first step [ 835 ], the IDP  810  sends a first message N 1  to the RPa  810 . N 1  is similar to M 1  apart from N 1  not including a proof token. Accordingly, while the RPa receives PII and associated PSP, it has no mechanism for enabling a second relying party, RPb  830 , to obtain the information. 
         [0046]    Consequently, according to the present example, the RPa  820  first checks that the PSP would permit information to be shared with the RPb [ 840 ]. If yes, the RPa  820  generates and sends a request message N 2  to the IDP  810 . N 2  includes an identifier I RPb , identifying RPb, which is signed by the RPa using its own signing key S RPa , and encrypted using the public encryption key E IDP  of the IDP  810 . 
         [0047]    The IDP  810  receives the request message N 2  and establishes [ 850 ] by reference to the PSP that the RPa  820  is allowed to enable the RPb  830  to obtain PII. In the answer is yes, the IDP  810  generates a response message N 3 . N 3  includes a proof token T RPb  that is bound to the RPb  830 . In the present example, T RPb  takes the general form {TokenRef, I RPb } E IDP , where TokenRef is a unique identifier as before generated by the IDP  810  and I RPb  is the identity of the intended relying party RPb  830 . In this way, it can be seen that T RPb  binds a specified destination relying party, in the present instance RPb  830 , to the TokenRef in a way that can only be revealed by the IDP  810 . Finally, N 3  is encrypted with the public encryption key E RPa . 
         [0048]    In a next step, the RPa  820  generates a message N 5 , which is equivalent to M 2  in  FIG. 7 . Steps  860 ,  865 ,  870 ,  875  and  880  are analogous to the steps  745 ,  750 ,  755 ,  760  and  765 , and will not be described again for reasons of brevity only. 
         [0049]    An important distinction according to the process in  FIG. 8 , when compared to the process in  FIG. 7 , is that the IDP  810 , and hence the user, know in advance that the RPb  830  has the potential to request the PII, even if RPb after receiving the proof token from RPa subsequently chooses not to submit a respective request. 
         [0050]    According to embodiments of the invention, the first protocol illustrated in  FIG. 7  can be adapted not to use proof tokens by, instead, arranging for the RPa  620  to pass the PII directly to the RPb  730  in step  745 . In this case, the PII would typically be encrypted using a public key and passed by the RPa, in encrypted form, to the RPb  730 , and the RPb would need to interact with the IDP  610  to obtain a respective decryption key, which can only be generated by the IDP. In either case, however, the PII is effectively revealed to the RPb, either by being unlocked (decrypted) after receipt or by being delivered in encrypted but decipherable form. This is an example where an Identifier Based Encryption (IBE) scheme could be employed to impose conditions that control RPb&#39;s access to the user&#39;s information. The conditions may be based on the user privacy preferences and may also include extra conditions that RPa wishes to impose, for example “access only permitted after a future date or time”. According to the IBE scheme, the conditions would represent a policy that is used as the encryption key, with the IDP subsequently generating and using (and providing) the corresponding decryption key or requested information. A disadvantage of such a protocol is that the RPa can send actual PII, albeit in encrypted form, directly to the RPb without any kind of notification to the IDP  610  or the user. The IDP  610  and user would only know the information transfer had occurred if the RPb subsequently submits a request for the decryption key. From a privacy perspective, it is typically preferable for all transactions to be recorded by the IDP  610 . However, an advantage of the protocol is that the IDP only needs to send the PII once (to the RPa), with subsequent requests involving only transmission of decryption keys. Of course, if there are many potential RPb for a given RPa, the RPa may prefer to send only a proof token to each RPb in order to reduce the volume of information it needs to send. Also, if there is a risk that the PII may become out of date before it is accessed by the RPb, if may be preferable, again, to rely on use of proof tokens. 
         [0051]    As described above, the examples illustrated herein are based on a federated architecture. In a particularly convenient embodiment, a known federated identity management system can be adapted for use according to the invention. Examples of federated identity management systems include OpenID &lt;http://openid.net/&gt;, Liberty Alliance &lt;http://www.projectliberty.org/&gt;, Higgins &lt;http://www.eclipse.org/higgins/&gt; and identity card schemes like Windows CardSpace &lt;http://netfx3.com/content/WindowsCardspaceHome.aspx&gt;. 
         [0052]    For example, embodiments of the present invention can adapt and apply CardSpace. CardSpace already enables users to store PII with selected, trusted identity providers. These providers may in general be any person or organisation which users trust and relying parties are willing to trust. IDPs may be banks, stores, or bespoke identity providers. The CardSpace application operates with the Windows operating system and controls the provision of a user&#39;s PII to relying parties. Relying parties can request PII in the form of identity cards, containing personal information. For example, a relying party with whom the user is interacting on-line to buy a product may request a CardSpace card accredited by a certain bank or other financial institution. In response, the CardSpace application will identify if the user has such a card and then interact with the respective bank to obtain either the PII (signed by the bank) or a proof token, of the kind described above. As it stands, there is no mechanism in CardSpace to facilitate and track the passing of information by a first relying party to a second or subsequent relying party. In other words, CardSpace is based on a three corner model, in which there is no provision for user preferences, for example PSP, to be evaluated and acted on by an IDP. However, by adapting CardSpace cards to include such user preferences, and enforcing IDPs to check the preferences and generate evidence of requests from relying parties (first, second or subsequent), users can be provided with an improved and flexible system which facilitates the protocols and processes at least as exemplified in  FIGS. 7 and 8 . 
         [0053]    In applying the CardSpace application to embodiments of the present invention, information fields in a user&#39;s PII are presented in the form of so-called CardSpace ‘Claims’. In this context, Claims are information fields that the IDP has accredited and claim to be true and accurate. With respect to  FIGS. 7 and 8 , references in the message protocol to PII would be replaced by those CardSpace Claims that are allowed, according to the PSP, to be passed to first, second and subsequent relying parties. 
         [0054]    The above embodiments are to be understood as illustrative examples of the invention. Further embodiments of the invention are envisaged. For example, in all embodiments, PII, Claims or equivalent can be passed from a first relying party to a second relying party directly in encrypted form, and then revealed to the second relying party by it acquiring a respective decryption key from an IDP. Alternatively, as described in detail herein, PII, Claims or equivalent can be passed to a second relying party directly (in unencrypted form) by an IDP, in response to the second relying party presenting the IDP with a legitimate proof token. As described, the proof token may be a general one, which is bound to the identity of the first relying party and passed automatically to the first relying party, or it may be a specific one, provided in response to a request from the first relying party, which particularly identifies the second relying party. In addition, with regard to capturing and storing evidence of information requests (as illustrated in  FIGS. 6 ,  7  and  8 ), this is clearly an important feature of embodiments of the present invention, which allows a user to establish whether a relying party is trustworthy, and which may influence how (or if) the user would trust a particular relying party in future. However, in other embodiments, it may not be a requirement that this kind of evidence is captured and stored, for example, if there is sufficient trust by the user of the information provider. In other embodiments, evidence may be collected selectively, for example, it may only be necessary to capture evidence of unauthorised requests or requests that, for whatever reason, cannot be completed, or requests that rely on tokens that are beyond an acceptable ‘use-by’ date, or only for requests that use a token from a second (or subsequent) relying party (or requestor), or the like. Obviously, many different criteria dictating whether or not to capture evidence of requests may be conceived on the basis of the disclosure herein. It is to be understood that any feature described in relation to any one embodiment may be used alone, or in combination with other features described, and may also be used in combination with one or more features of any other of the embodiments, or any combination of any other of the embodiments. Furthermore, equivalents and modifications not described above may also be employed without departing from the scope of the invention, which is defined in the accompanying claims.