A Security Assessment of Trusted Platform Modules

Trusted Platform Modules (TPMs) are becoming ubiquitous devices included in newly released personal computers. Broadly speaking, the aim of this technology is to provide a facility for authenticating the platform on which they are running: they are able to measure attest to the authenticity of a hardware and software configuration. Designed to be cheap, commodity devices which motherboard and processor vendors can include in their products with minimal marginal cost, these devices have a good theoretical design. Unfortunately, there exist several practical constraints on the effectiveness of TPMs and the architectures which employ them which leave them open to attack. We demonstrate some hardware and software attacks against these devices and architectures. These attacks include Time of Check/Time of Use attacks on the Integrity Measurment Architecture, and a bus attack against the Low Pin Count bus. Further we explore the possibility of side-channel attacks against TPMs.