Abstract: Recent years have witnessed the rapid growth of mobile computing environments. One of the major concerns in such environments is security, specially in the context of wireless communications. We describe some of the important issues which need to be addressed in designing a security scheme for mobile communications. These include autonomy of communicating entities, mobility of the users, limitations of the hardware, etc. We describe a scheme which addresses the above issues, and provides a correct and efficient mechanism to establish secure communications. Our scheme provides authentication of the communicating entities, location privacy, and secure messaging.