Utilizing I-V non-linearity and analog state variations in ReRAM-based security primitives

The underlying variability in the ReRAM device operation, while undesired in many applications, can be advantageous for hardware security primitives. ReRAM devices also come with the advantage of having non-linear multi-state operation. By comparison with previous reported ReRAM PUFs, which utilized spatial variations in the devices' binary ON/OFF states, we proposed to use sneak path currents and device / network nonlinearity as its main source of randomness to implement robust, reconfigurable and dense security primitives. In particular, in this work we present an in-depth discussion of how device non-linearity is affected by the read bias and the thermal stresses applied to the ReRAM crossbar. For the experimental demonstration, we used a three-dimensional stack of two 10×10 Al
2
O
3
/TiO
2−x
-based ReRAM crossbars with good uniformity for the memristors in both crossbar layers. The results highlight the utility of device non-linearity to extract more complex and more reliable one-way functions from relatively small ReRAM crossbar arrays.