Implementing geo-encryption in GSM cellular network

The “geo-encryption” or “location-based encryption” is a security algorithm that limits the access or decryption of information content to specified locations and/or times. This algorithm does not replace any of the conventional cryptographic algorithms, but instead adds an additional layer of security to exist stack. GSM is chosen as a case study to implement geo-encryption in its key generation part due to its many properties that are beneficial to this protocol. GSM´s BTSs are distributed across the network and their signal can reach places like urban canyons and indoor environments inside the network. In GSM, data stream between mobile subscriber (MS) and BTS is encrypted by A5 encryption algorithm. A5´s encryption and decryption key (k_c) is generated base on MS´s SIM card parameter (k_i) and a random number, RAND. At this project we have used MS´s location information to generate this key by geo-encryption algorithm idea. Encrypted data only in the MS´s location, that just GSM network is aware of it, can be decrypted and its accuracy depends on used positioning algorithm.