Traditional methods for message authentication are based on the cryptographic verification of received data using some sort of a shared secret. While this task is not critical for traditional networks, Wireless Sensor Networks (WSNs) may pay a high price for the gained protection - sensor nodes are forced to invest their already scarce resources in receiving a message and executing cryptographic computations, only to discard the message afterwards in case of a failed authentication. This work introduces a different, crypto-free approach for enabling authenticated communication by leveraging peculiarities of wireless communication, in particular its broadcast nature and the feasibility of channel capacity jamming. Instead of receiving and then verifying transmitted data, sensor nodes are prevented from receiving fake data at all. This is achieved by coupling physical characteristics of signal propagation with legitimate transmissions. Such a coupling enables the detection and invalidation of impersonation attacks by using short jamming pulses emitted by surrounding WSN nodes. We justify this concept by designing a novel communication protocol explicitly integrating the jamming feature, and analyze factors which impact the efficiency of successful jamming, such as the frame length, transmission timing accuracy, and various other issues identified through extensive empirical measurements.
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