Because of the additional screening required to ensure entropy, Xilinx offers two versions of the
PUF, a 128-bit and a 256-bit. In both cases, the KEK length is 256 bits. These devices require special ordering codes (SCD). The PUF is not supported for the standard ordering codes, except for development and evaluation, as there is no assurance that there is sufficient entropy in the
KEK. Entropy is measured as described in Zynq UltraScale+ MPSoC PUF Characterization Report
(RPT236) [Ref 6] which is a Xilinx proprietary report. Contact your local Xilinx FAE or sales
person to obtain a copy of the report. Use of the PUF does not require additional licensing fees.