IACR News item: 08 June 2015
Qinglong Zhang, Zongbin Liu, and Cunqing Ma, Changting Li, Jiwu Jing
ePrint Report(PUF) on FPGAs is crucial and popular for its nice properties and easy
implementation. The compensated measurement based on the ratio of
two ring oscillators\' frequencies proves to be particularly effective to extract
entropy of process variations. However from two ring oscillators
only one bit entropy is extracted and RO PUFs will occupy numerous
resource with the size of private information increasing. Motivated by this
inefficient resource usage, we propose an elegant and efficient method to
extract at least 31 bits entropy from two ring oscillators on FPGAs by
utilizing the fine control of programmable delay lines (PDL). We call this
construction Further ROPUF (FROPUF). In this paper, we present in
detail how to take advantage of the underlying random process variation
which derives from the lookup tables (LUT) of two ring oscillators,
and show that the in-depth variation can be extracted by a similar second
order difference calculation. In addition, we reveal the consistency
of the evaluation results from Xilinx FPGAs (e.g. Virtex-5, Virtex-6,
Kintex-7) and those by simulation of FROPUF. The responses of our
new construction have a nominal bit-error-rate (BER) of 1.85% at 27
◦
C
and FROPUF greatly promotes the number of entropy with equivalent
reliability of the general ROPUF.
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