PUFs – An Extensive Survey




Ravishankar, Yamini

Journal Title

Journal ISSN

Volume Title



Physical Unclonable Functions (PUFs) offer a promising solution to the issue of secure key generation on chips for cryptographic applications. For a given challenge, PUFs generate a response, unique to the device based on its inherent manufacturing variations, which is why PUFs are the biometrics of Integrated Circuits (ICs). Ring-Oscillator based PUFs (RO-PUFs) are a type of Silicon-based PUF that exploit the delay in interconnects and components of the design to generate unique keys. Configurable RO-PUFs (CRO-PUFs) reduce the number of ROs needed to generate a key of a given length compared to the RO-PUFs. This thesis is an extensive survey of the history of PUFs – implementations and applications, and the evaluation, post-processing and attack methodologies. A CRO-PUF exploiting the delay of latches in the Configurable Logic Blocks (CLBs) of Spartan6 FPGAs was implemented on 20 Nexys3 boards. The statistical properties of the obtained responses indicated a Steadiness of 94.6% and a Uniformity of 46.7% respectively. A novel proposal of using Hidden-Markov Models for post-processing of PUF responses for increased reliability is being made as a result of cross-disciplinary study of biometrics with hardware cryptography.



Physical unclonable functions, Secure key generation, PUF constructions, Hardware cryptography, Hidden Markov Models, Ring-Oscillator based PUF