Embodiments of the present disclosure provide intrinsic program suppression of a non-programmed two-terminal resistive switching memory cell of a plurality of memory cells defining an identifier bit, such as a physical unclonable feature (PUF) bit. Differential programming applies a program signal to a plurality of resistive switching memory cells and derives a value for the identifier bit from which cell(s) becomes programmed. However, where more than an expected number of cells become programmed, an invalid value can occur. Disclosed intrinsic program suppression mitigates or avoids the invalid result by very rapidly reducing the program signal to a non-programmed cell(s) in response to another cell(s) becoming programmed. In an embodiment, intrinsic program suppression can be implemented by programming the plurality of memory cells electrically in parallel and shorting second terminals of the plurality of memory cells at a common node.