performing a tilt test on a physical unclonable function (PUF) cell of a transistor circuitry, comprising tilting said PUF cell at least once, and comparing a mismatch magnitude of said PUF cell to a tilt threshold;

determining a magnitude of said mismatch, wherein a mismatch magnitude below said tilt threshold is considered a first logic value and a mismatch magnitude above said tilt threshold is considered a second logic value, and

wherein said mismatch magnitude of said PUF cell is random; and using said absolute value of said mismatch magnitude as an entropy source to produce at least one PUF bit called a mirror PUF bit.