Scalable PHY-Layer Security for Distributed Detection in Wireless Sensor Networks

Abstract

Abstract-The problem of binary hypothesis testing is considered in a bandwidth-constrained densely populated low-power wireless sensor network operating over insecure links. Observations of the sensors are quantized and encrypted before transmission. The encryption method maps the output of the quantizer to one of the possible quantizer output levels randomly according to a probability matrix. The intended (ally) fusion center (AFC) is aware of the encryption keys (probabilities) while the unauthorized (third party) fusion center (TPFC) is not. A constrained optimization problem is formulated from the point of view of AFC in order to design its decision rule along with the encryption probabilities. The objective function to be minimized is the error probability of AFC and the constraint is a lower bound on the error probability of TPFC. In the binary case the optimal solution is found and in the nonbinary case a good suboptimal solution is analytically obtained. Numerical results are presented to show that it is possible to degrade the error probability of TPFC significantly and still achieve very low probability of error for AFC. The proposed method which may be considered a PHY-layer security scheme is highly scalable since it does not increase the packet overhead or transmit power of the sensors and has very low computational complexity. A scheme is described to randomize the keys so as to defeat any key space exploration attack.Index Terms-Decentralized detection, decision fusion rule, information security, soft decision, wireless sensor networks.

Secure Distributed Detection under Energy Constraint in IoT-Oriented Sensor Networks

“…But the processing capability of the EFC was too limited. Another category of effective scheme is the probabilistic ciphering based one, where the sensor’s observation is randomly mapped to a set of quantization levels according to an optimal mapping probabilities matrix [9,24,25]. However, the security is assured by assuming the EFC being completely ignorant about the mapping probabilities.…”

“…However, the sensors’ transmissions are overheard by the EFC, who also wishes to detect the target state. From the literature [2,7,9], we have seen that the stochastic ciphering could be employed to protect the information of the sensors from the EFC efficiently, since each sensor would flip its decision randomly and the EFC would be confused when it was ignorant about the flipping probability (i.e., the encryption key). However, the key exchange between the AFC and the sensor itself may be not secure from the EFC.…”

“…random variables. Then, invoking the central limit theorem [9,23], we can deem that the statistic of ${\mathrm{normal\Lambda }}^A$ converges to a normal distribution for a large K . That is ${\mathrm{\Lambda }}^A|{\theta }_i\sim \mathrm{scriptN}({\mu }_{Ak}|{\theta }_i,\frac{{\gamma }_{Ak}^2|{\theta }_i}{K})$, where ${\mu }_{Ak}|{\theta }_i$ and ${\gamma }_{Ak}^2|{\theta }_i$ are the mean and variance of ${\mathrm{normal\Lambda }}_k^A$ conditioned on ${\theta }_i$, respectively.…”

“…Aiming to the spectrum scarcity problem, some enhanced technologies with high spectrum efficiency are advocated, for example, the cognitive Internet of Things (CIoT) who introduces the cognitive radio technology to the IoT network [5]. A decentralized inference network where the nodes transmit the compressed observations to reduce the required bandwidth is another solution [7], and the distributed detection technique utilized in sensor networks is a typical instance [8,9,10,11]. Since a huge number of devices are included in IoT, the energy to be spent for communication and computation is extremely large and improving energy efficiency becomes more important.…”

“…For the practical resource constraints and the serious security issues in front of WSN, secure distributed detection schemes under energy constraints are necessary for the development of an efficient IoT. Various secure strategies for distributed detection have been proposed under different assumptions on the eavesdroppers and transmission channels [8,9,10,23,24,25,26,27,28,29]. However, these studies focused on either the local detection at sensors or the information transmission from sensors to the FC.…”