Implementation of Ring Oscillators Based Physical Unclonable Functions with Independent Bits in the Response

International audienceThe paper analyzes and proposes some enhancements of Ring Oscillators based Physical Unclonable Functions (PUFs). PUFs are used to extract a unique signature of an integrated circuit in order to authenticate a device and/or to generate a key. We show that designers of RO PUFs implemented in FPGAs need a precise control of placement and routing and an appropriate selection of ROs pairs to get independents bits in the PUF response. We provide a method to identify which comparisons are suitable when selecting pairs of ROs. Dealing with power consumption, we propose a simple improvement that reduces the consumption of the PUF published by Suh et al. in 2007 by up to 96.6%. Last but not least, we point out that ring oscillators significantly influence one another and can even be locked. This questions the reliability of the PUF and should be taken into account during the design

Delay-based Physical Unclonable Function Implementation

As we venture further into the 21st century, it becomes much clearer that hardware security is at the forefront of many challenges that we face today in ensuring that data is protected. “Keys” (a sequence of bits) can be used to unlock pieces of data and is a concept that is pervasive throughout cryptography, but storage in memory makes this sole method nonviable. To make the approach more practical, one can dynamically generate a key through a Physical Unclonable Function (PUF). PUFs are circuit primitives that use intrinsic variations of microchips created during the manufacturing process to generate a unique “fingerprint” for each chip. We simulated several different PUF designs on a Field Programmable Gate Array (FPGA) board to determine how changes to a starting design can affect the reliability, randomness, and uniqueness of these IDs. We propose two schemes, a parallel and a serial scheme for a ring oscillator (RO) based PUF. The parallel scheme is a useful benchmark for other designs, and the serial scheme uses much less hardware than other RO PUF designs. The serial scheme is not as random, reliable, or unique as the parallel scheme, but it creates input-output pairs with much less area