Following this verification operation of the acquired marker, the sentinel establishes the state of the authentication operation (for example “accepted” or “rejected”). Once this state is established, the authentication operation is over. The departure stage allows for shutting down this procedure and gracefully moving to the next one. We now need to consider what uses we want to make of identity once we rigorously established it.

Differential identity of the potential participants in a transaction is a central characteristic of policy; that is, policy may be ascribed to identities as well as to transactions. In particular, provision of policy as an aspect of both parties of a transaction, requiring negotiation between the two prior to a transaction is absent from most, if not all identification systems today. In the application of identity concepts and identification systems, it is typically the case that the use of identity is more the purview of the receiver of identity rather than the provider of identity. Consequently, there is diminished concern regarding whether identifiers through which the identity of people is ostensibly authenticated are compromised, and hence can be used by other people to impersonate the identity of the true target of the identifiers. Through this theft of identity, an attacker can perform any action or make any claim that the impersonated person could perform or make if they were physically present and participating in the transaction in question. This obviously points out a huge problem with such identification systems and leads one to consider at least partially alleviating this problem through the provision of user controlled policy definition mechanisms.

Specifically, the policy through which the use of identity is established must be expanded in law and then provided for within identification systems. That is, the ultimate source of the policy should either be general law or it should be the result of a negotiation between the provider and the receiver of identity on a transaction by transaction basis. There are a wide range of issues from which policy could be defined under the personal control of each individual with the definition of policy itself being related to the strength of the authentication mechanism used to establish the differential identity of a person. Authentication protocols can range from high trust variants, perhaps requiring a person to go to an office equipped with very secure and accurate biometric sensors, to low trust variants, perhaps only requiring a person to present a contactless token at a turnstile. Policy allowing for making use of varying levels of security for entry of authentication parameters (biometrics, personal identification numbers, etc.) allows for a variety of performance levels when an identity token is presented as well as a variety of trust levels in the resulting authentication.

Through policy definition, it can be specified what trust can the receiver place in materials or services attested to by a specific authenticated identity. For example, a person may want to disavow any trust being placed in casual e-mail messages. Today, the perception in some circles may be that an e-mail message is akin to a highly trusted, absolutely truthful document to which the signer attests, under pain of liability. Other people, however, may consider e-mail to be a highly informal mode of communication, worthy at one extreme of simply passing along gossip. So, it should be possible for a person to establish a policy regarding the trustworthiness of specific messages and allow the sending and received to negotiate a well-defined policy for the sending and receiving of messages. If one side attests only to passing along unsubstantiated gossip, and the other side doesn’t want to hear any such gossip, then no exchange takes place.

The processes through which the interactions supported by a policy infrastructure proceed can take on a variety of forms aimed at a variety of purposes. We have just spent some effort looking at the most general of the interaction protocols, that of authentication of the entities which will engage in the interaction. After authentication, we are able to ascribe specific aspects of policy to

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