Offloading cryptographic services to the SIM card in smartphones

Smartphones have achieved ubiquitous presence in people’s everyday life as communication, entertainment and work tools. Touch screens and a va- riety of sensors offer a rich experience and make applications increasingly diverse, complex and resource demanding. Despite their continuous evolu- tion and enhancements, mobile devices are still limited in terms of battery life, processing power, storage capacity and network bandwidth. Computa- tion offloading stands out among the efforts to extend device capabilities and face the growing gap between demand and availability of resources. As most popular technologies, mobile devices are attractive targets for malicious at- tackers. They usually store sensitive private data of their owners and are increasingly used for security sensitive activities such as online banking or mobile payments. While computation offloading introduces new challenges to the protection of those assets, it is very uncommon to take security and privacy into account as the main optimization objectives of this technique. Mobile OS security relies heavily on cryptography. Available hardware and software cryptographic providers are usually designed to resist software attacks. This kind of protection is not enough when physical control over the device is lost. Secure elements, on the other hand, include a set of protections that make them physically tamper-resistant devices. This work proposes a computation offloading technique that prioritizes enhancing security capabilities in mobile phones by offloading cryptographic operations to the SIM card, the only universally present secure element in those devices. Our contributions include an architecture for this technique, a proof-of-concept prototype developed under Android OS and the results of a performance evaluation that was conducted to study its execution times and battery consumption. Despite some limitations, our approach proves to be a valid alternative to enhance security on any smartphone.