1. A computer system for virtual attribute federation, the computer system comprising: a memory medium comprising program instructions; a bus coupled to the memory medium; and a processor for executing the program instructions comprising a virtual attribute federation manager (VAFM), the instructions causing the system to: sign an instance of a virtual attribute and a value calculation method with a signature; federate the instance of the virtual attribute across each of a plurality of virtual attribute enabled directories (VAEDs) by mapping, for the virtual attribute according to the value calculation method, a federated instance external to the VAEDs to a local instance internal to the VAEDs, wherein at least one of the VAEDs is in a different domain than at least one other of the VAEDs; and execute, at each VAED, in response to a recognition by the VAED of the signature, the virtual attribute and value calculation method in a restricted environment, the restricted environment being abstracted by a resource map and external ports and the restricted environment preventing the value calculation method from at least one of: transmitting information outside of the VAED, reading information outside of the VAED except through the set of external ports, changing information in the attribute store, and accessing information that an executing user identity does not have access to from outside the VAED.