Computing systems designed using reconfigurable hardware are increasingly composed using a number of different Intellectual Property (IP) cores, which are often provided by third-party vendors that may have different levels of trust. Unlike traditional software where hardware resources are mediated using an operating system, IP cores have fine-grain control over the underlying reconfigurable hardware. To address this problem, the embedded systems community requires novel security primitives that address the realities of modern reconfigurable hardware. In this work, we propose security primitives using ideas centered around the notion of “moats and drawbridges.” The primitives encompass four design properties: logical isolation, interconnect traceability, secure reconfigurable broadcast, and configuration scrubbing. Each of these is a fundamental operation with easily understood formal properties, yet they map cleanly and efficiently to a wide variety of reconfigurable devices. We carefully quantify the required overheads of the security techniques on modern FPGA architectures across a number of different applications.

A protection profile for high-robustness separation kernels has recently been validated and several implementations are under development. However, medium-robustness separation kernel development efforts have no protection profile, although the US Government has published guidance for authoring such a profile. As a step toward a protection profile, a set of security requirements for medium-robustness separation kernels is proposed. These requirements result from an informal, yet principled, approach. By bracketing the problem with appropriate reference points and elaborating a method for interpolating the requirements both a measure of uniformity and a basis for further discussion are achieved. Our reference points include the high robustness protection profile, the existing medium robustness consistency instruction, and our familiarity with the nuances of separation kernels. This practitioner-oriented study is intended to advance the prevailing practices for commercial software development, which presently falls far short of the rigor needed for either high-robustness or medium-robustness systems. These requirements represent an incremental improvement in the pursuit of secure software - and is intended to be a step forward on the road to higher assurance.

Blurring the line between software and hardware, reconfigurable devices strike a balance between the raw high speed of custom silicon and the post-fabrication flexibility of general-purpose processors. While this flexibility is a boon for embedded system developers, who can now rapidly prototype and deploy solutions with performance approaching custom designs, this results in a system development methodology where functionality is stitched together from a variety of "soft IP cores," often provided by multiple vendors with different levels of trust. Unlike traditional software where resources are managed by an operating system, soft IP cores necessarily have very fine grain control over the underlying hardware. To address this problem, the embedded systems community requires novel security primitives which address the realities of modern reconfigurable hardware. We propose an isolation primitive, moats and drawbridges, that are built around four design properties: logical isolation, interconnect traceability, secure reconfigurable broadcast, and configuration scrubbing. Each of these is a fundamental operation with easily understood formal properties, yet maps cleanly and efficiently to a wide variety of reconfigurable devices. We carefully quantify the required overheads on real FPGAs and demonstrate the utility of our methods by applying them to the practical problem of memory protection.