Physical layer security

This presentation captures the historical adaptation of medieval warriors’ methods for security and thwarts toward adversarial attacks on fortifications for protective areas. History can often be a good teacher for modern day designers for security protection because the evolution of human beings has not changed since the beginning of time. Applicable lessons are applied to all aspects of security to include physical, technical, personnel, information and operational security. The article provides examples of the original concept of access controls, vaulted areas, chemical warfare, and the origins of physical security.

We study the problem of physical layer security in massive multiple-input multiple-output (MaMIMO) cognitive radio networks (CRNs). In particular, we investigate the design of a smart jamming attack on the uplink transmission of a CRN in the presence of a single antenna jammer. The jammer is aware of the transmission protocol as well as the pilot set used for channel training in the MaMIMO systems. It attacks both the training and data transmission phases but with different powers. To have the most destructive attack, the jammer optimally divides its power between two phases to minimize the maximum energy efficiency of the secondary system. The resulting power optimization is a non-convex problem and to solve it, we propose a method to transform it into a convex optimization problem. Numerical results illustrate the effectiveness of the proposed smart jamming attack in decreasing the energy efficiency of the secondary MaMIMO system.

Long range wide area network (LoRaWAN) is one of the most widely used low power wide area (LPWA) network technologies in the unlicensed ISM bands. LoRaWAN adopts chirp spread spectrum (CSS) based physical layer specification which is Semtech's proprietary technology; so the details of the physical layer are not fully disclosed. In this paper, we will investigate the performance of the LoRa interleaver which is one of the main blocks of LoRa physical layer. Specifically, through computer simulations, we will compare a conventional block interleaver and the LoRa interleaver in terms of FER performance in AWGN and Rician fading environments.

Secrecy capacity is a fundamental informationtheoretic performance metric to predict the maximum data rate
of reliable communication, while the intended message is not
revealed to the eavesdropper. Motivated by this consideration,
in this paper a unified communication-theoretic framework for
the analysis of the probability of non-zero secrecy capacity, the
secrecy outage probability and the secrecy capacity of multipleantenna systems over fading channels is proposed. Specifically,
a powerful frequency-domain approach is first developed, in
which the integrals involved in the evaluation of the probability
of non-zero secrecy capacity and secrecy outage probability are
transformed into the frequency domain, by employing Parseval’s
theorem. A generic approach for the evaluation of the asymptotic
secrecy outage probability at high signal-to-noise ratio (SNR)
region is also introduced, thus providing useful insight as to the
parameters affecting the secrecy performance. Finally, a unified
numerical approach for computing the average secrecy capacity
of multiple-antenna systems under arbitrary fading environments is developed. The proposed framework is general enough
to accommodate any well-known multi-antenna transmission
technique and fading model. Finally, the secrecy performance
of several multiple-antenna system setups is assessed, in the
presence of generalized fading conditions and arbitrary antenna
correlation, while various numerical and computer simulation
results are shown and compared to substantiate the proposed
mathematical analysis

In this letter, the system performance of the DF full-duplex (FD) relaying communication network is investigated with physical layer security (PLS). In this system model, the source (S) and the destination (D) communicate via a helping relay (R) in the presence of the eavesdropper (E). From the system model, we derive the closed-form expressions for intercept probability (IP) and secrecy outage probability (SOP). For verifying the correctness of the analytical analysis, the Monte Carlo simulation is conducted. In addition, the influence of the main system parameter on the system performance is investigated. Finally, the results show that the analytical and the simulation values agree well with each other.

In this work, we take on the role of a wireless adversary and investigate one of its most powerful tools---radio frequency jamming. Although different jammer designs are discussed in the literature, reactive jamming, i.e., targeting only packets that are already on the air, is generally recognized as a stepping stone in implementing optimal jamming strategies. The reason is that, while destroying only selected packets, the adversary minimizes its risk of being detected. One might hope for reactive jamming to be too challenging or uneconomical for an attacker to conceive and implement due to its strict real-time requirements. Yet, in this work we disillusion from such hopes as we demonstrate that flexible and reliable software-defined reactive jamming is feasible by designing and implementing a reactive jammer against IEEE 802.15.4 networks. First, we identify the causes of loss at the physical layer of 802.15.4 and show how to achieve the best performance for reactive jamming. Then, we apply these insights to our USRP2-based reactive jamming prototype, enabling a classification of transmissions in real-time, and reliable and selective jamming. The prototype achieves a reaction time in the order of microseconds, a high precision (such as targeting individual symbols), and a 97.6% jamming rate in realistic indoor scenarios for a single reactive jammer, and over 99.9% for two concurrent jammers.

In this paper, a novel secure data transmission method called interference signal superposition-aided multiple-input multiple-output with antenna number modulation and adaptive antenna selection (ISS-MIMO-ANM-AAS) is presented to defend transmission systems against eavesdropping attacks or to share secret information between two communication parties in scenarios, where perfect secrecy and ultimate confidentiality are required to be achieved. In the proposed method, while data is transmitted to the legitimate receiver by exploiting the features of MIMO-ANM through transmitting additional data bits with the number of active antennas along with those bits sent by using conventional M-PSK/QAM modulation, the data that the eavesdropper receives is aimed to be mixed by an interference signal superposed (ISS) with the original signal to eliminate the possible wiretapping activities. The conducted theoretical analysis along with the obtained numerical simulations for the proposed ISS-MIMO-ANM-AAS method proves the effectiveness of the scheme, where MIMO-ANM transmission is shown to be fully secured through the ISS algorithm. Thus, the introduced ISS-MIMO-ANM-AAS method can be considered a strong potential candidate method for scenarios where ultra-security is the main requirement of wireless systems including WiFi, 5G, 6G, and beyond technologies. The codes of this article can be found at https://researcherstore.com/product/simulation-codes-for-the-interference-signal-superposition-mimo-with-antenna-number-modulation-and-adaptive-antenna-selection-for-achieving-perfect-secrecy/
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The Matlab simulation codes used to generate the results in this paper can be found at https://researcherstore.com with the name ISS-MIMO-ANM. WISLAB (wislabi.com/solutions) offers solutions for building and deploying fully secure, cloud-based, and low-cost end-to-end 4G/5G networks along with providing consultations on helping companies reduce their networks CAPEX/OPEX cost and determine which solutions are best suited for their needs and use cases.

Encryption is the process of encoding messages in such a way, that they can only be decoded by the intended receiver. On the other hand, physical-layer (PHY) security exploits channel characteristics, such as noise and multipath fading, in order to ensure confidential transmission. Even though PHY security had initially been considered as an impractical theoretical concept with little application to reality, the continued improvement in the processing power of eavesdroppers’ devices has made encryption methods more vulnerable to cryptanalytic attacks. Therefore, both from an academic and an industrial point of view, PHY security has attracted considerable attention, due to its independence from the computational strength of the eavesdropper.
In this thesis, recent research efforts on PHY security are outlined, and novel mathematical expres- sions for problems related to PHY security are derived. Also, methods and algorithms are proposed, which aim to improve the performance of existing ones. The thesis is divided into three main parts.
The first part examines PHY security from an information-theoretic standpoint, by evaluating mea- sures, such as the secrecy capacity and the secrecy outage probability (SOP). Specifically, the impact of location uncertainty of the eavesdropper on PHY security in wireless systems is evaluated and quantified. A single-antenna downlink system with a single legitimate user and an eavesdropper is considered, and the eavesdropper’s location is modeled as a two-dimensional uniform distribution over a ring-shaped area around the base-station (BS). An exact, closed-form expression for the SOP is derived, as well as a simplified expression for the case of free-space transmission. Moreover, a closed-form expression for the SOP is derived for the case, where the distance between the BS and the eavesdropper is modeled as a one-dimensional uniform distribution from the inner to the outer radius of the ring. Insights are given and conclusions are drawn based on the offered results for the SOP. Next, the effect of interference on the SOP is investigated, in a single-antenna downlink system with a single legitimate user and an eavesdropper. An arbitrary number of broadcasting BSs, whose signals are treated by the legitimate receiver and the eavesdropper as interference, is assumed. Also, all the wireless links in the system are subject to Rayleigh fading. Under these assumptions, an exact, closed-form expression is derived for the SOP. Numerical results for the SOP are provided and conclusions are drawn.
The second part deals with PHY key exchange algorithms, and specifically ones that are based on multipath fading. First, a novel least-square channel thresholding process is presented, so that the transmitter and the legitimate receiver each generate a bit string, based on their respective channel responses. According to the principle of reciprocity, the two bit strings are almost identical. The proposed thresholding method leads to a larger number of series of consecutive ones in the generated bit strings, compared to the case where a constant threshold is used. It is demonstrated that, when this method is used in the context of a PHY key exchange algorithm, this property leads to better protection from eavesdropper attacks. Next, two error reconciliation methods are proposed, in order to correct the discrepancies between the bit strings generated by the transmitter and the legitimate receiver. The first method is based on a neural network, which is constructed and trained by the transmitter, so that inputs similar to its bit string are changed to the correct value. Afterwards, the receiver’s bit string is fed through the neural network, which corrects the bit discrepancies with the transmitter’s bit string. The second method uses block error correction coding, in order to perform error reconciliation. Also, the average number of consecutive ones is used in order to produce a mask, that increases the security of the method against brute-force attacks. The two methods are shown, through simulations, to have higher key agreement rates than other methods proposed in the literature.
The third part focuses on polar codes, and particularly the design of polar codes for the relay channel. An erroneous decoding detection method is proposed, which we refer to as “smart” relaying. This technique can be applied to a polar coding scheme, where successive cancellation decoding is used. Specifically, the log-likelihood ratios (LLRs) used at any point in the decoding process are compared with a threshold parameter, and if a decision is made by taking into consideration an LLR that is too close to 1, the decoded result is discarded. In this case, the relay does not retransmit the message, since it is more likely that the receiver will make the correct decision by only taking into consideration the information received from the direct source-destination channel. Otherwise, part of the information is re-encoded by the relay with a capacity-achieving polar code for the relay-destination channel, and re-transmitted to the destination. A combination of the information received by the source and the relay is used in order to reconstruct the original message. Furthermore, a condition is proven, that shows in which cases “smart” relaying yields a better block error rate, compared to the case where “smart” relaying is not used. An extension of this technique to multiple parallel relay systems is also proposed. Finally, simulation results are presented, in order to illustrate the performance of the proposed method.

LTE is an emerging wireless communication technology to provide high-speed data service for the mobile phones and data terminals. To improve indoor coverage and capacity Femtocells are included in 3GPP since Release 8. There is no common simulation platform is available for performance justification of LTE-Femtocells. LTE-Sim is an object-oriented open source simulator which incorporates a complete protocol stack can be used for simulating two-tier macro-femto scenarios. To the best of our knowledge no paper provides the guideline to perform system level simulation of Femtocell networks. Here, in this paper Femtocells performance is evaluated in multi-Macrocells and multi-Femtocells environment with interference from Microcells and Macrocell users along with the scripting. KEYWORDS Channel quality indicator (CQI), Femto Access Point (FAP), Macro eNodeB (MeNB), Macrocell User Equepment (MUE), Moblity Management Entity(MME), Signal to Interference Plus Noise Ratio(SINR), Physical Layer(PHY)

In this paper, we investigate the reliability and security performance of cooperative multi-relay systems, where both source and relay nodes are energy-constrained nonlinear energy harvesters, scavenging energy from a power beacon nearby. Our analysis is based on practical model since residual hardware impairments (RHIs) and channel estimation errors (CEEs) are considered. Aiming at improving the system efficiency, three representative relay selection strategies are considered: 1) random relay selection (RRS); 2) suboptimal relay selection (SRS); and 3) optimal relay selection (ORS). To characterize the security performance of the considered strategies, we derive closed-form analytical expressions of the reliability and security in terms of outage probability (OP) and intercept probability (IP). We further discuss the asymptotic expressions and scaling laws of OP with the number of relays. The IP is analyzed for non-colluding and colluding scenarios. The numerical results illustrate that: 1) There is a tradeoff between reliability and security, that is when the outage constraint is relaxed, the IP can be enhanced, and vice versa; ii) The outage performance of the ORS and SRS schemes outperform RRS, indicating that relay selection can enhance reliability performance; iii) There are error floors for the OP due to the CEEs; iv) Colluding eavesdroppers can enhance eavesdropping attacks by sharing their intercepted information; and v) Although RHIs and CEEs have deleterious effects on the OP, they can protect the information transmission against eavesdropping attacks. INDEX TERMS Physical layer security, hardware impairments, nonlinear energy harvesters, relay selection, reliability-security tradeoff.

Even though the wireless network of 5G has not been investigated exhaustively, the sixth generation (6G) echo systems' visionaries are already being debated. Therefore, to solidify and consolidate privacy and security within 6G networks, this paper examines edge computing and its convergence with blockchain in 6G: security challenges. Moreover, the paper examines how security might affect the wireless systems of the 6G, potential obstacles characterizing various 6G technologies, alongside possible remedies. This paper unveils the 6G security vision alongside key indicators of performance with tentative landscape threat premised upon predicted sixth generation infrastructure. Furthermore, a discussion of the privacy and security challenges that might emerge from the existing sixth generation applications and demands is presented. Additionally, the paper sheds light into the researchlevel projects and standardization efforts. Specific attention is accorded to discussion on the security consideration with 6G enhancing technologies, including quantum computing, visible light communication (VLC), distributed ML/AI, physical layer security, and distributed ledger technology (DLT). Overall, this paper seeks to guide the subsequent investigation of sixth generation privacy and security in the early stage of envisioning to practicality.

This research work has investigated the physical layer security of both MISO and OFDM-MIMO communication systems. This project explored the use of beamforming and artificial noise generation as transmit strategy to achieve secure communication. In the MISO system, a probabilistic approach for achieving secrecy was studied. This method ensures a target probability of secrecy characterised by QoS constraint at the eavesdropper and the legitimate receiver. Further, this research work considers the optimum power allocation strategy between the information signal and artificial noise. Results from MATLAB simulation show that this scheme achieves the target probability of secrecy by allocating the minimum power for both constrained and unconstrained transmit power scenarios. It was established that for

With the current technology revolution, underwater wireless sensor networks (UWSNs) find several applications such as disaster prevention, water quality monitoring, military surveillance and fish farming. Nevertheless, this kind of networks faces a number of challenges induced by the nature of the underwater environment and its influence on the network physical media. Therefore, the ultimate objective of this paper is to lay down the key aspects of the physical layer of the underwater sensor networks (UWSNs). It discusses issues related to the characteristics and challenges of the underwater communication channel, differences between terrestrial wireless sensor networks and UWSNs, and acoustic propagation models in underwater. The paper also surveys some of the underwater acoustic modems. This study is essential to better understand the challenges of designing UWSNs and alleviate their effects.

In  this  paper
proposes
security  issues  and  its  solution  for  WiMAX  network.  Jamming  and  Scrambling  is  main  security  issues  regarding
Physical Layer. The lack of Physical infrastructure of wireless networks is inherently less secure. In this paper propose se
curity issues and its solution for
WiMAX network. Jamming and Scrambling is main security issues regarding Physical Layer. The lack of Physical infrastructure o
f wireless networks is
inherently less secure. The performance analysis of the WiMAX system has
been carried out for single and multicarrier jamming. It has been found that
the performance of the system varies significantly with different jamming signals. The performance of the WiMAX system has be
en studied under the
influence of the basis of Modulat
ion schemes (QPSK, BPSK, 16 QAM and 64 QAM), Types of antennas (Sector antenna, Omni directional antenna and
isotropic antenna) and Throughput on the basis of number of subcarriers destroyed. On the basis of simulation results and per
formance analysis foun
d
that  the  performance  of  BPSK  and  QPSK  is  better  than  other  modulation  scheme  under  single  carrier  jamming.  WiMAX  sector  anten
na  gives  better
performance than isotropic and WiMAX Omni antennas. Throughput is reduced when data subcarriers are destroyed in
uplink and downlink.  Uplink is
more  sensitive  to  data  subcarrier  reduction  compare  to  downlink.  The  performance  of  the  downlink  PUSC  is  better  than  uplink  P
USC  under  the
influence of the multicarrier jamming.

IJHMI - ASDFJournals.com

This paper presents a secure beamforming design
to prevent eavesdropping on multiple-input multiple-output
(MIMO) device-to-device (D2D) communication. The devices
communicate via a trusted relay which performs physical layer
network coding (PNC), and multiple eavesdroppers are trying
to intercept the device information. The beamforming design is
based on minimizing mean square error of the D2D communication
while employing signal-to-interference-plus-noise ratio
(SINR) threshold constraints to prevent possible eavesdropping.
The channel state information of the device-to-eavesdropper and
relay-to-eavesdropper channels is imperfect at the devices and
relay. The channel estimation errors are assumed with Gaussian
Markov uncertainty model. Consequently, robust optimization
problems are formulated considering the multiple access and
broadcasting stages of the D2D communication. These problems
are non-convex, and two algorithms are proposed to solve them.
In the numerical analysis, we discuss the convergence of the
proposed algorithms, impact of the number of eavesdroppers on
the performance, and the SINR distributions at eavesdroppers.

The future wireless communication systems demand much more enhanced security and reliability compared to currently deployed systems. In this work, we propose a much simpler yet more efficient physical layer security (PLS) technique for achieving reliable and secure communication in the multiple-input single-output non-orthogonal multiple access (MISO-NOMA) systems. This system is capable of providing enhanced confidential communication as well as inter-user interference cancellation without using the successive interference cancellation (SIC) method. The conventional NOMA was previously adopted under the name of multiuser superposition transmission (MUST) in release 13 of 3GPP but recently excluded from 3GPP-release 17 due to its performance degradation. In this work, we analyze the drawbacks in conventional NOMA and present a new kind of NOMA with more improved performance metrics. The proposed algorithm combines the benefit of pre-coder matrices with simultaneous transmission using antenna diversity to provide simple, reliable, and secure communication without complex processing at the receivers in downlink scenarios. The effectiveness of the proposed algorithm is verified and proven by extensive analysis and numerical simulations.

The future wireless communication systems demand enhanced security and reliability than the current systems. In this work, we propose a more simple yet efficient physical layer security (PLS) technique for achieving reliable and secure communication in the multiple-input single-output non-orthogonal multiple access (MISO-NOMA) system. This system is capable of providing enhanced confidential communication as well as inter-user interference cancellation without using the successive interference cancellation (SIC) method. As conventional NOMA was already adopted under the name of multi-user superposition transmission (MUST) in release 13 of 3GPP and is improved in terms of receiver design for 3GPP-release 16, which still suffers from several security risks and drawbacks. In this work, we have analyzed these drawbacks and presented a new kind of NOMA with better performance results in cases where conventional NOMA fails. The proposed algorithm combines the benefit of pre-coder matrices with simultaneous transmission using antenna diversity to provide simple, reliable, and secure communication without complex processing at the receivers in downlink scenarios. The effectiveness of the proposed algorithm is verified and proven by extensive numerical simulations.

—In this paper, we investigate secure device-to-device
(D2D) communication in energy harvesting large-scale cognitive
cellular networks. The energy constrained D2D transmitter
harvests energy from multi-antenna equipped power beacons
(PBs), and communicates with the corresponding receiver using
the spectrum of the primary base stations (BSs). We introduce a
power transfer model and an information signal model to enable
wireless energy harvesting and secure information transmission.
In the power transfer model, three wireless power transfer
(WPT) policies are proposed: 1) cooperative power beacons
(CPB) power transfer, 2) best power beacon (BPB) power
transfer, and 3) nearest power beacon (NPB) power transfer.
To characterize the power transfer reliability of the proposed
three policies, we derive new expressions for the exact power
outage probability. Moreover, the analysis of the power outage
probability is extended to the case when PBs are equipped
with large antenna arrays. In the information signal model, we
present a new comparative framework with two receiver selection
schemes: 1) best receiver selection (BRS), where the receiver
with the strongest channel is selected, and 2) nearest receiver
selection (NRS), where the nearest receiver is selected. To assess
the secrecy performance, we derive new analytical expressions
for the secrecy outage probability and the secrecy throughput
considering the two receiver selection schemes using the proposed
WPT policies. We presented Monte-carlo simulation results to
corroborate our analysis and show: 1) secrecy performance
improves with increasing densities of PBs and D2D receivers
due to larger multiuser diversity gain, 2) CPB achieves better
secrecy performance than BPB and NPB but consumes more
power, and 3) BRS achieves better secrecy performance than
NRS but demands more instantaneous feedback and overhead.
A pivotal conclusion is reached that with increasing number of
antennas at PBs, NPB offers a comparable secrecy performance
to that of BPB but with a lower complexity.

—We investigate beamforming and artificial noise generation at the secondary transmitters to establish secure transmission in large scale spectrum sharing networks, where multiple non-colluding eavesdroppers attempt to intercept the secondary transmission. We develop a comprehensive analytical framework to accurately assess the secrecy performance under the primary users' quality of service constraint. Our aim is to characterize the impact of beamforming and artificial noise generation (BF&AN) on this complex large scale network. We first derive exact expressions for the average secrecy rate and the secrecy outage probability. We then derive an easy-to-evaluate asymptotic average secrecy rate and asymptotic secrecy outage probability when the number of antennas at the secondary transmitter goes to infinity. Our results show that the equal power allocation between the useful signal and artificial noise is not always the best strategy to achieve maximum average secrecy rate in large scale spectrum sharing networks. Another interesting observation is that the advantage of BF&AN over BF on the average secrecy rate is lost when the aggregate interference from the primary and secondary transmitters is strong, such that it overtakes the effect of the generated AN.

As the latest member of the multiple access family, non-orthogonal multiple access (NOMA) has been recently proposed for 3GPP Long Term Evolution (LTE) and envisioned to be an essential component of 5th generation (5G) mobile networks. The key feature of NOMA is to serve multiple users at the same time/frequency/code, but with different power levels, which yields a significant spectral efficiency gain over conventional orthogonal MA. This article provides a systematic treatment of this newly emerging technology, from its combination with multiple-input multiple-output (MIMO) technologies, to cooperative NOMA, as well as the interplay between NOMA and cognitive radio. This article also reviews the state of the art in the standardization activities concerning the implementation of NOMA in LTE and 5G networks.

Considering the advancements of the internet of things (IoT) in 6G and beyond communications , data transmission security in IoT devices has received extensive interest because of their significant features, such as low computational complexity, led by low power requirements. In such devices, the conventional cryptographic techniques may fail to provide secure communication. To fight this drawback, physical layer security (PLS) has remarkable potential to provide security solutions suitable for such applications. In this work, a highly effective PLS technique is proposed for providing secure communication against external and internal eavesdroppers in a downlink multi-cell, multiuser , and multi-carrier IoT communication system. In our proposed system, we considered two base stations, where each base station uses a single radio frequency (RF) chain to link two antennas that are used for the transmission of data. Further, we transmit the data in two rounds, and each round of transmission occurs through a single active antenna of each base station. A different antenna is used for each round of transmission to communicate with two single antenna IoT devices/users in the presence of a passive eavesdropper. In the proposed algorithm, frequency selective channel-based pre-coder matrices and the dual transmission approach are jointly employed. The dual-transmission is performed simultaneously from two base stations to provide security against internal and external eavesdroppers. The proposed system is suitable for IoT-based applications. Also, the potential capabilities of our proposed algorithm are proved by extensive mathematical and simulation analysis.

We consider the multiple-input multiple-output (MIMO) wiretap channel under a minimum receiver-side power constraint in addition to the usual maximum transmitter-side power constraint. This problem is motivated by energy harvesting communications with wireless energy transfer, where an added goal is to deliver a minimum amount of energy to a receiver in addition to delivering secure data to another receiver. In this paper, we characterize the exact secrecy capacity of the MIMO wiretap channel under transmitter and receiver-side power constraints. We first show that solving this problem is equivalent to solving the secrecy capacity of a wiretap channel with a double-sided correlation matrix constraint on the channel input. We show the converse by extending the channel enhancement technique to our case. We present two achievable schemes that achieve the secrecy capacity: the first achievable scheme uses a Gaussian codebook with a fixed mean, and the second achievable scheme uses artificial noise (or cooperative jamming) together with a Gaussian codebook. The role of the mean or the artificial noise is to enable energy transfer without sacrificing from the secure rate. This is the first instance of a channel model where either the use of a mean signal or use of channel prefixing via artificial noise is strictly necessary in the MIMO wiretap channel.

We propose a new secure underwater acoustic communication scheme designed to let a user (Alice) transmit a confidential message to another user (Bob) in the presence of an eavesdropper (Eve). A typical approach in conventional wireless physical-layer security is to rely on a friendly jammer to jam Eve through artificial noise (AN). Instead, for the first time, we propose a secure underwater communication scheme that relies on cooperative friendly jamming through CDMA-based analog network coding (ANC). The cooperative friendly jammer transmits information using the same spreading code used in the legitimate Alice-Bob link. The information transmitted by the cooperative jammer is known a priori to Bob, but not to Eve. Although the jammer's packet will also interfere at Bob, we show that after jointly estimating the two multipath-affected channels, Bob can suppress the interfering packet and decode Alice's packet, while Eve cannot. We also formulate the problem of joint optimal selection of friendly jammer and power allocation (for Alice and the jammer) that minimize Eve's capability of intercepting the signal while guaranteeing a predefined level of quality of service (QoS) for Bob. The proposed scheme is implemented in a testbed based on Teledyne Benthos Telesonar SM-975 underwater modems and tested extensively in Lake LaSalle at the University at Buffalo. Experiments and simulations demonstrate that, for a given energy budget, the proposed scheme can guarantee much higher bit error rate (BER) at Eve, while creating minimal BER disturbance at Bob, compared to the ANaided approach.

Securing wireless sensor networks (WSNs) is a hard problem. In particular, network access control is notoriously difficult to achieve due to the inherent broadcast characteristics of wireless communications: an attacker can easily target any node in its transmission range and affect large parts of a sensor network simultaneously. In this paper, we therefore propose a distributed guardian system to protect a WSN based on physically regulating channel access by means of selective interference. The guardians are deployed alongside a sensor network, inspecting all local traffic, classifying packets based on their content, and destroying any malicious packet while still on the air. In that sense, the system tries to gain "air dominance" over attackers. A key challenge in implementing the guardian system is the resulting real-time requirement in order to classify and destroy packets during transmission. We present a USRP2 software radio based guardian implementation for IEEE 802.15.4 that meets this challenge; using an FPGA-based design we can even check for the content of the very last payload byte of a packet and still prevent its reception by a potential victim mote. Our evaluation shows that the guardians effectively block 99.9% of unauthorized traffic in 802.15.4 networks in our experiments, without disturbing the legitimate operations of the WSN.

This paper tackles the problem of generating shared secret keys based on the physical characteristics of the wireless channel. We propose intelligent quantization mechanisms for key generation, achieving high secret bits generation rate. Moreover, some practical issues affecting the performance of the key generation mechanism are deeply investigated. Mainly, we investigate the effects of delay and mobility on the performance and we enhance the key generation mechanism accordingly. As a result, this paper presents a framework towards robust key generation from multipath wireless channels.

In this work, to overcome the flaws of standard chaotic maps we generated two new cascaded structures, 3D Cubic-Sine and 2D Cubic-Cat chaotic parametric maps, based on a new parameter-varied Cubic map that enhance the chaos complexity and therefore offering a high randomness’s level of the chaotic sequences and a huge key space.To provide optimum security for image transmission, we introduce several methods with a new approaches in Stenography and encryption of quadrature amplitude modulation symbols (QAM)based on the new maps, all in a purpose of enhancement physical layer security. Some of the best results obtained are: the peak signal-to-noise ratio (PSNR) values of 96.2956 dB, 88.767 dB, 78.1094 dB respectively with the three methods, also the entropy of encrypted image reaching much closely the ideal value, being 8 ≈ 7.9999868, strong resistance against differential attack with Number of Pixels Change Rate (NPCR) of 99.63%, Unified Average Changing Intensity (UACI) of 33.54% and high speed ciphering based on 3D Cubic-Sine noise encryption time of 0.024s.The experimental results indicate that these new maps outperforms the most competitive recently proposed maps in multimedia cryptosystems.

In this work, to overcome the flaws of standard chaotic maps we generated two new cascaded
structures, 3D Cubic-Sine and 2D Cubic-Cat chaotic parametric maps, based on a
new parameter-varied Cubic map that enhance the chaos complexity and therefore offering
a high randomness’s level of the chaotic sequences and a huge key space.To provide optimum
security for image transmission, we introduce several methods with a new approaches
in Stenography and encryption of quadrature amplitude modulation symbols (QAM)based
on the new maps, all in a purpose of enhancement physical layer security. Some of the best
results obtained are: the peak signal-to-noise ratio (PSNR) values of 96.2956 dB, 88.767 dB,
78.1094 dB respectively with the three methods, also the entropy of encrypted image reaching
much closely the ideal value, being 8 ≈ 7.9999868, strong resistance against differential
attack with Number of Pixels Change Rate (NPCR) of 99.63%, Unified Average Changing
Intensity (UACI) of 33.54% and high speed ciphering based on 3D Cubic-Sine noise encryption
time of 0.024s.The experimental results indicate that these new maps outperforms the
most competitive recently proposed maps in multimedia cryptosystems.

We focus on a scenario where two wireless source nodes wish to exchange confidential information via an RF energy harvesting untrusted two-way relay. Despite its cooperation in forwarding the information, the relay is considered untrusted out of the concern that it might attempt to decode the confidential information that is being relayed. To discourage the eavesdropping intention of the relay, we use a friendly jammer. Under the total power constraint, to maximize the sum-secrecy rate, we allocate the power among the sources and the jammer optimally and calculate the optimal power splitting ratio to balance between the energy harvesting and the information processing at the relay. We further examine the effect of imperfect channel state information at both sources on the sum-secrecy rate. Numerical results highlight the role of the jammer in achieving the secure communication under channel estimation errors. We have shown that, as the channel estimation error on any of the channels increases, the power allocated to the jammer decreases to abate the interference caused to the confidential information reception due to the imperfect cancellation of jammer's signal.

—The broadcast nature of the wireless medium allows unintended users to eavesdrop the confidential information transmission. In this regard, we investigate the problem of secure communication between a source and a destination via a wireless energy harvesting untrusted node which acts as a helper to relay the information; however, the source and destination nodes wish to keep the information confidential from the relay node. To realize the positive secrecy rate, we use destination-assisted jamming. Being an energy-starved node, the untrusted relay harvests energy from the received radio frequency signals, which include the source's information signal and the destination's jamming signal. Thus, we utilize the jamming signal efficiently by leveraging it as a useful energy source. At the relay, to enable energy harvesting and information processing, we adopt power splitting (PS) and time switching (TS) policies. To evaluate the secrecy performance of this proposed scenario, we derive analytical expressions for two important metrics, viz., the secrecy outage probability and the ergodic secrecy rate. The numerical analysis reveals the design insights into the effects of different system parameters like power splitting ratio, energy harvesting time, target secrecy rate, transmit signal-to-noise ratio (SNR), relay location, and energy conversion efficiency factor, on the secrecy performance. Specifically, the PS policy achieves better optimal secrecy outage probability and optimal ergodic secrecy rate than that of the TS policy at higher target secrecy rate and transmit SNR, respectively.

Wireless communications are increasingly important in health-care applications, particularly in those that use
implantable medical devices (IMDs). Such systems have many
advantages in providing remote healthcare in terms of monitoring, treatment and prediction for critical cases. However, the
existence of malicious adversaries, referred to as nodes, which
attempt to control implanted devices, constitutes a critical risk
for patients. Such adversaries may perform dangerous attacks
by sending malicious commands to the IMD, and any weakness
in the device authentication mechanism may result in serious
problems including death. In this paper we present a physical
layer (PHY) authentication technique for IMDs that does not
use existing methods of cryptology. In addition to ensuring
authentication, the proposed technique also provides advantages
in terms of decreasing processing complexity of IMDs and
enhances overall communications performance.

Key management in wireless sensor networks does not only face typical, but also several new challenges. The scale, resource limitations, and new threats such as node capture and compromise necessitate the use of an on-line key generation, where secret keys are generated by the nodes themselves. However, the cost of such schemes is high since their secrecy is based on computational complexity. Recently, several research contributions justified that the wireless channel itself can be used to generate information-theoretic secure keys between two parties. By exchanging sampling messages during movement, a bit string can be derived that is only known to the involved entities. Yet, movement is not the only possibility to generate randomness. The channel response is also strongly dependent on the frequency of the transmitted signal. In our work, we introduce a protocol for key generation based on the frequency-selectivity of channel fading. The great practical advantage of this approach is that we do not rely on node movement as the source of randomness. Thus, the frequent case of a sensor network with static motes is supported. Furthermore, the error correction property of the proposed protocol mitigates the effects of measurement errors and other temporal effects, giving rise to a key agreement rate of over 97%. We show the applicability of our protocol by implementing it on MICAz motes, and evaluate its robustness and secrecy through experiments and analysis.

Due to the enormous spreading of applied wireless networks, security is actually one of the most important issues for telecommunications. One of the main issue in the field of securing wireless information exchanging is the initial common knowledge between source and destination. A shared secret is normally mandatory in order to decide the encryption (algorithm or code or key) of the information stream. It is usual to exchange this common a priori knowledge by using a "secure" channel. Nowadays a secure wireless channel is not possible. In fact normally the common a priori knowledge is already established (but this is not secure) or by using a non-radio channel (that implies a waste of time and resource). This contribution deals with the proposal of a new modulation technique ensuring secure communication in a full wireless environment. The information is modulated, at physical layer, by the thermal noise experienced by the link between two terminals. A loop scheme is designed for unique recovering of mutual information. The probability of error/detection is analytically derived for the legal users and for the third unwanted listener (passive or active attacker). Both the case of passive and active attacks have also been implemented and simulated by using Matlab-Simulink software. The analytical results have been compared to the simulated ones. All the results show that the performance of the proposed scheme yields the advantage of intrinsic security, i.e., the mutual information cannot be physically demodulated (passive attack) or denied (active attack) by a third terminal.

We analyze the secrecy outage performance of a mixed radio frequency-free space optical (RF-FSO) transmission system with imperfect channel state information (CSI). We deal with a single-input multiple-output (SIMO) wiretap model, where a base station (works as the relay) forwards the signal transmitted from a user (source) to a data center (works as the destination), while an eavesdropper wiretaps the confidential information by decoding the received signal. Both the relay and the eavesdropper are armed with multiple antennas and maximal ratio combining scheme is utilized to improve the received signal-to-noise ratio (SNR). The effects of imperfect CSI of the RF link and the FSO link, misalignment, detection schemes, and relaying schemes on the secrecy outage performance of mixed RF-FSO systems are studied. Firstly, the cumulative distribution function and probability density function of FSO links with pointing error and two different detection technologies are derived. Then we derive the closed-form expressions for the lower bound of the secrecy outage probability (SOP) with fixed-gain relaying and variable-gain relaying schemes. Furthermore, asymptotic results for SOP are investigated by exploiting the unfolding of Meijer's G-function when the electrical SNR of FSO link approaches infinity. Finally, Monte-Carlo simulation results are presented to corroborate the correctness of the analysis.

Recent advances in spectrum access technologies, such as cognitive radios, have made spectrum sharing a viable option for addressing the spectrum shortage problem. However , these advances have also contributed to the increased possibility of " hacked " or " rogue " radios causing harm to the spectrum sharing ecosystem by causing significant interference to other wireless devices. One approach for countering such threats is to employ a scheme that can be used by a regulatory entity (e.g., FCC) to uniquely identify a transmitter by authenticating its waveform. This enables the regulatory entity to collect solid evidence of rogue transmissions that can be used later during an adjudication process. We coin the term Blind Transmitter Authentication (BTA) to refer to this approach. Unlike in the existing techniques for PHY-layer authentication, in BTA, the entity that is authenticating the waveform is not the intended receiver. Hence, it has to extract and decode the authentication signal " blindly " with little or no knowledge of the transmission parameters. In this paper, we propose a novel BTA scheme called Frequency o↵set Embedding for Authenticating Transmitters (FEAT). FEAT embeds the authentication information into the transmitted waveform by inserting an intentional frequency o↵set. Our results indicate that FEAT is a practically viable approach and is very robust to harsh channel conditions. Our evaluation of FEAT is based on theoretical bounds, simulations, and indoor experiments using an actual implementation.