A method for creating a physical unclonable function (PUF) bit for use with transistor circuitry includes performing a tilt test on a PUF cell of a transistor circuitry, comprising tilting the PUF cell at least once, and comparing a mismatch of a response of the PUF cell to a tilt threshold. A magnitude of the mismatch is determined. A mismatch magnitude below the tilt threshold is considered a first logic value” and a mismatch magnitude above the tilt threshold is considered a second logic value. The mismatch magnitude of the PUF cell is random. The absolute value of the mismatch magnitude is used as an entropy source to produce at least one PUF bit called a mirror PUF bit.