Fast DRAM PUFs on Commodity Devices

Intrinsic physical unclonable functions (PUFs), which derive hardware identifiers from components already present in a system without modification, are an appealing way to add a layer of hardware rooted security into a system. This is evidenced by the fact that the majority of PUF designs in commercial use today are intrinsic. However, as each intrinsic PUF design is reliant on specific hardware their use is limited to a subset of systems. It is therefore desirable to have practical intrinsic PUF designs for as wide a range of underlying hardware as possible. Most intrinsic PUF designs to date have used memory as the entropy source, with the most well studied type being based on SRAM. More recently designs based on DRAM have been proposed, an appealing prospect considering the ubiquity of that technology. While previous research has demonstrated that entropy can be extracted from DRAM there has not yet been a substantive demonstration of such a PUF operating in real-time on a commodity system. In this article, we present a novel set of algorithms for deriving PUF responses in-runtime from DRAM by altering timing parameters using only software. These algorithms reduce the critical period of system disruption by 96% from 88 ms to 3 ms on average compared to existing designs. We present a large scale dataset derived from 1824 DRAM chips characterized using the proposed design on commodity off-the-shelf desktop hardware running a Linux OS. An analysis of the data shows that in addition to the speed improvements the proposed design shows near ideal (>44%) uniqueness and good (>88%) reliability.