1. A token-based centralized authentication and data retrieval method for providing access to a service provider to user information associated with a user's relationship with the service provider, comprising the steps of: authenticating using a user token a user presenting the user token at a user terminal, the user token having stored thereon a user ID; deriving a resource identifier using at least two data input elements, the at least two data input elements including the user ID of the user and a service provider ID of the service provider, wherein the user information is stored in a storage network and the resource identifier is associated with the user information, wherein the user ID and service provider ID are separately received by an authentication system in communication with the storage network, wherein the authentication system performs the step of deriving the resource identifier using the user ID and service provider ID; retrieving the user information from the storage network using the resource identifier; and providing the retrieved user information to the service provider, the method further comprising the steps of: issuing from the authentication system a temporary transaction identifier to one of the user terminal and a service provider agent, the temporary transaction identifier being associated with an access or authentication request; receiving the temporary transaction identifier from the other of the user terminal and the service provider agent; and performing the resource identifier deriving step after receiving the temporary transaction identifier at the authentication system.