Towards customizable, application specific mobile trusted modules

Abstract

Two different security extensions of mobile platforms for hosting Mobile Trusted Module (MTM) functionality have been introduced in recent years: the ARM TrustZone processor extension and Secure Elements. Both approaches can host MTMs which are typically designed as a static and fixed set of functions. However, with the increasing number of supported functions, the complexity of these MTMs is being raised and with it the resource requirements on the hosting security extension. Disembedding MTM functionality and dynamic loading of TPM commands can be a solution to reduce these requirements. In order to address this problem, we propose and analyze two approaches for providing modular, customizable MTM functionality which are based on currently available cell phones' security extensions. We propose two architectures in order to overcome the resource limitations of existing approaches and show how secure and dynamic command loading architectures can be established with the ARM TrustZone extension and Secure Elements.