A logical building block and method of using the building block to design a logic cell library for CMOS (Complementary Metal Oxide Silicon) ASICs (Application Specific Integrated Circuits) is disclosed. Different logic gates, built with the same building block as described in this invention, will have the same schematics of transistor connection and also the same physical layout so that they appear to be physically identical under optical or electron microscopy. An ASIC designed from a library of such logic cells is strongly resistant to a reverse engineering attempt.