Providing mobile network security is disclosed. A first mobile network provider equipment registers using a secret data that is known to a registration entity with which the first mobile network provider equipment is configured to register and embodied in a physical device associated with the first mobile network provider equipment in a manner that enables the physical device to be used to perform a cryptographic function using the secret data but prevents the physical device from being used to provide the secret data as output. An encryption data usable to communicate securely with a second mobile network provider equipment over a packet data network is received from the registration entity.