cryptography is used to generate a token that both authorizes request processing and establishes constraints on that authorization . a mobile communications device user or client subscribes to an information service of a content provider . a description of the subscribed service is generated . the client applies a digital signature to the description and optionally encrypts the signed description . a token is generated based on the signed description . the content provider presents the token to the request processing entity of a mobile service provider in order to establish trust between the content provider and the request processing entity . the request processing entity decrypts the token and verifies the signature of the client . the request of the content provider is validated through a comparison of the request with the constraints indicated in the decrypted token . valid requests are processed . for example , a request for location information about the client is fulfilled in order for the content provider to push a local weather report to the mobile device of the client .