Design of A Ring Oscillator Based PUF with Enhanced Challenge Response pair and Improved Reliability

Hardware security is of utmost importance nowadays, with the increased number of threats like modelling attacks, reverse engineering and extracting secret information from the IC's. A physical unclonable function (PUF) is a promising solution to many security related problems and can be used to produce devices or IC's that are unique and resistant to cloning attempts. A PUF is like a fingerprint for a particular physical object, it is based on many manufacturing mismatches that occur during IC fabrication or the propagation delays that are present in the wires and interconnects. Various kinds of PUF designs are possible like ring oscillator, SRAM and arbiter PUF's etc. A Ring oscillator based PUF is designed based on the delays present in the wires that leads to different frequency of oscillation and can form the basis for key generation. They are also easily implemented in field programmable gate array (FPGA).In this paper we propose a ring oscillator based design with enhanced challenge response pair (CRP) with improved reliability. Our design has more number of challenge response pair since all the possible frequency comparisons of the Ro are done. Also it provides better reliability because our approach relies on relative values and not absolute value, it incorporates the difference between the highest frequency in the present comparison and the maximum of all the measured frequencies, under varying environmental conditions even if the absolute value changes, the relative value will never change.