Apparatus comprising (190; 200; 210; 290; 310; 320): a PUF-film comprising: a flat circuit structure (32; 154) comprising a plurality of circuit elements (26; 152); and a flat electric shield; wherein the circuit structure (32; 154) is evaluable with respect to a plurality of electric capacitance values (34 1,2, 34 2,3) being arranged between the plurality of circuit elements (26; 152); and wherein the electric shield at least partially covers the circuit structure (26; 152) and provides for a common reference electrode of the plurality of electric capacitance values(34 1,2, 34 2,3); the apparatus further comprising an evaluation unit configured for providing electrical excitation signals in antiphase with respect to each other to provide for an antiphasic excitation of neighbored circuit elements (26; 152) and for differentially evaluating the plurality of electric capacitance values (34 1,2, 34 2,3) based on the antiphasic excitation of the neighbored circuit elements; wherein the plurality of circuit elements (26; 152) comprises a multitude of conductive traces, wherein the PUF-film is evaluable with respect to an electric capacitance value (34 1,2, 34 2,3) between a first conductive trace and a second conductive trace, wherein the PUF-film comprises a capacitive element (166 1) being galvanically connected to the first conductive trace (152 1) and the second conductive trace (152 2). a PUF-film comprising: a flat circuit structure (32; 154) comprising a plurality of circuit elements (26; 152); and a flat electric shield; wherein the circuit structure (32; 154) is evaluable with respect to a plurality of electric capacitance values (34 1,2, 34 2,3) being arranged between the plurality of circuit elements (26; 152); and wherein the electric shield at least partially covers the circuit structure (26; 152) and provides for a common reference electrode of the plurality of electric capacitance values(34 1,2, 34 2,3); a flat circuit structure (32; 154) comprising a plurality of circuit elements (26; 152); and a flat electric shield; wherein the circuit structure (32; 154) is evaluable with respect to a plurality of electric capacitance values (34 1,2, 34 2,3) being arranged between the plurality of circuit elements (26; 152); and wherein the electric shield at least partially covers the circuit structure (26; 152) and provides for a common reference electrode of the plurality of electric capacitance values(34 1,2, 34 2,3); the apparatus further comprising an evaluation unit configured for providing electrical excitation signals in antiphase with respect to each other to provide for an antiphasic excitation of neighbored circuit elements (26; 152) and for differentially evaluating the plurality of electric capacitance values (34 1,2, 34 2,3) based on the antiphasic excitation of the neighbored circuit elements; wherein the plurality of circuit elements (26; 152) comprises a multitude of conductive traces, wherein the PUF-film is evaluable with respect to an electric capacitance value (34 1,2, 34 2,3) between a first conductive trace and a second conductive trace, wherein the PUF-film comprises a capacitive element (166 1) being galvanically connected to the first conductive trace (152 1) and the second conductive trace (152 2).