An Authentication Federation Proxy Which Conceals Attributes and Authorization Policies Each Other

A mechanism for privacy-enhanced authentication and authorization federation is proposed. The mechanism conceals attributes of a user provided by the IdP from the SP, and simultaneously conceals an authorization policy of a service presented by the SP from the IdP. The mechanism is implemented as an authentication federation proxy which works between an IdP and an SP. Attributes of a user is provided to the proxy by the IdP and an authorization policy is presented to the proxy by the SP, but both of the attributes and the authorization policy are scrambled. The proxy can determine whether the given attributes match the policy but it can neither know the detail of attributes nor the policy.