CarINA - Car Sharing with IdeNtity Based Access Control Re-enforced by TPM

Car sharing and car access control from mobile devices is an increasingly relevant topic. While numerous proposals started to appear, practical deployments ask for simple solutions, that are easy to implement and yet secure. In this work we explore the use of TPM 2.0 functionalities along with identity-based signatures in order to derive a flexible solution for gaining access to a vehicle. While TPM 2.0 specifications do not have support for identity-based primitives we can easily bootstrap identity-based private keys for Shamir's signature scheme from regular RSA functionalities of TPM 2.0. In this way, key distribution becomes more secure as it is re-enforced by hardware and the rest of the functionalities can be carried from software implementations on mobile phones and in-vehicle controllers. We test the feasibility of the approach on modern Android devices and in-vehicle controllers as well as with a recent TPM circuit from Infineon.