embodiment of the invention the passivation layer 102 contains an inhomogeneous characteristic i e a plurality of randomly distributed conducting particles 104 which can be evaluated by the chip 100 autonomously i e by a puf detector 110 which also forms part of the chip 100 during production of the chip 100 a reference value representing the expected evaluation result of the puf may be stored in the chip 39 s internal non volatile memory not shown an attempt to remove the passivation layer 102 for example in case of reverse engineering of the chip 100 will irreversibly damage the puf i e the random structure of conducting particles 104 and the evaluation result of the puf will permanently deviate from the expected result thus the chip 100 may evaluate the puf by means of the puf detector 110 and compare the evaluation result with the reference value in order to determine whether or not the passivation layer 102 has been removed if the passivation layer 102 is removed and or replaced the change can be detected by the chip 100 autonomously in a relatively easy way pufs implemented by poorly matching devices like small diodes or transistors have the disadvantage that they usually do not notice a modification of the top or bottom surface of the chip while a protection of these parts against unnoticed modification would raise the security hardness of the chip pufs using the properties of the surface such as optical or electrical properties are difficult to implement a puf implemented by randomly distributed conducting particles 104 in the passivation layer 102 of the chip 100 protects the surface of the chip 100 in combination with a relatively easy detection scheme fig2 shows a method of producing a.