Bit string analysis of Physical Unclonable Functions based on resistance variations in metals and transistors

Security mechanisms such as encryption, authentication and feature activation depend on the integrity of embedded secret keys. The mechanism by which these `digital secrets' are stored within Integrated Circuits (ICs) is changing from EPROMs and/or fuse technology to Physical Unclonable Functions (PUFs). PUFs leverage the naturally occurring manufacturing variations within each IC to produce repeatedly random digital identifiers. In this paper, we analyze the quality of the bit strings generated by PUFs that leverage resistance variations in 1) the power grid metal wires and transistor on-resistance in 60 copies of a 90 nm chip and 2) in the power grid metal wires of 58 copies of a 65 nm chip.