Our society greatly depends on services and applications provided by mobile communication networks. As billions of people and devices become connected, it becomes increasingly important to guarantee security of interactions of all players. In this talk we address several aspects of this important, many-folded problem. First, we show how to design cryptographic primitives which can assure integrity and confidentiality of transmitted messages while satisfying resource constrains of low-end low-cost wireless devices such as sensors or RFID tags. Second, we describe countermeasures which can enhance the resistance of hardware implementing cryptographic algorithms to hardware Trojans.