Hardware assistance for trustworthy systems through 3-D integration

Hardware resources are abundant; state-of-the-art processors have over one billion transistors. Yet for a variety of reasons, specialized hardware functions for high assurance processing are seldom (i.e., a couple of features per vendor over twenty years) integrated into these commodity processors, despite a small flurry of late (e.g., ARM TrustZone, Intel VT-x/VT-d and AMD-V/AMD-Vi, Intel TXT and AMD SVM, and Intel AES-NI). Furthermore, as chips increase in complexity, trustworthy processing of sensitive information can become increasingly difficult to achieve due to extensive on-chip resource sharing and the lack of corresponding protection mechanisms. In this paper, we introduce a method to enhance the security of commodity integrated circuits, using minor modifications, in conjunction with a separate integrated circuit that can provide monitoring, access control, and other useful security functions. We introduce a new architecture using a separate control plane, stacked using 3D integration, that allows for the function and economics of specialized security mechanisms, not available from a co-processor alone, to be integrated with the underlying commodity computing hardware. We first describe a general methodology to modify the host computation plane by attaching an optional control plane using 3-D integration. In a developed example we show how this approach can increase system trustworthiness, through mitigating the cache-based side channel problem by routing signals from the computation plane through a cache monitor in the 3-D control plane. We show that the overhead of our example application, in terms of area, delay and performance impact, is negligible.