  The unique identities of every mobile user (phone number,IMSI) and device
(IMEI) are far from secure and are increasingly vulnerable to a variety of
network-level threats. The exceedingly high reliance on the weak SIM
authentication layer does not present any notion of end-to-end security for
mobile users. We propose the design and implementation of Secure Mobile
Identities (SMI), a repetitive key-exchange protocol that uses this weak SIM
authentication as a foundation to enable mobile users to establish stronger
identity authenticity. The security guarantees of SMI are directly reliant on
the mobility of users and are further enhanced by external trusted entities
providing trusted location signatures (e.g. trusted GPS, NFC synchronization
points). In this paper, we demonstrate the efficacy of our protocol using an
implementation and analysis across standard mobility models.
