Mapping Obfuscation-Based PHY Security Scheme for Resource-Constrained Wireless Sensor Network

Wireless sensor network (WSN) physical layer (PHY) uses M-ary spread spectrum (MaSS). This paper explores MaSS and emphasizes that based on the implementation approach; the technology has the potential to provide security at the PHY of wireless devices. The MaSS parameters, namely, spreading sequences and symbol to sequence mapping logic, can be obfuscated for security implementation. In this paper, we have focused our analysis on obfuscating mapping logic, i.e. Mapping Obfuscation (MO). Mathematical analysis reveals that an eavesdropper with processing speed in the order of 10(18) operations/sec can intercept and decode short length (maximum 8-10 bytes) packets in <100 s. Simulation exposes that the eavesdropper can achieve a success rate of 50% for short-length packets if its signal-to-noise ratio exceeds -1 dB. An attacker has only one check metric for mapping sequence detection that is correct frame check sequence (FCS) detection. However, FCS detection may be misleading; if packet-embedded FCS and eavesdropper-generated FCS are the same for the wrong mapping sequence. For MO-based MaSS, false FCS detection probability is 30 times more than valid FCS detection probability. To reduce false FCS probability attacker need to analyse multiple radio frequency (RF) packets for detecting a valid mapping key; this increases the computation time. For MO-based PHY security, correct mapping sequence identification by exhaustive search demands cluster-based parallel processing.