Information-theoretic Secrecy Research Articles

Joint Information-Theoretic Secrecy and Covertness for UAV-Assisted Wireless Transmission With Finite Blocklength

In this paper, we study a novel joint information-theoretic secrecy and covertness model for an unmanned aerial vehicle (UAV)-assisted finite blocklength transmission system, in which an UAV delivers classified information to a ground user (Bob) in the presence of two unauthorized users (Eve and Willie). Specifically, Eve tries to decode the legitimate information while Willie tries to detect if the UAV's transmission is present or not. Firstly, we assume that the perfect location knowledge of both Eve and Willie is known at the UAV. In this scenario, to guarantee security and covertness, the average secrecy rate maximization problem is formulated via joint design of the UAV's transmit power and three dimensional (3D) trajectory under Willie's covertness constraint. Technically speaking, the optimization problem is non-convex and mathematically intractable to tackle owing to the coupling of multiple variables. To address this non-convex problem, an iterative alternating optimization (AO) algorithm is developed with the assistance of the successive convex approximation (SCA) technique. After that, we extend the system model to both Eve's and Willie's imperfect location knowledge case, which is more sophisticated compared to the perfect location knowledge case due to the uncertain location constraints. We still utilize the iterative AO algorithm combined with SCA and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\mathcal {S}$</tex-math></inline-formula> -procedure techniques to cope with the nonconvex problem. Numerical results indicate that our proposed 3D optimization algorithm performs better than the conventional two dimensional (2D) scheme and the benchmark scheme for both perfect and imperfect location knowledge cases.

PERFORMANCE ANALYSIS OF A POINT-TOPOINT SYSTEM UNDER ACTIVE ATTACK

—In wireless communications, security issues have become difficult due to unchangeable and unpredictable nature of the wireless medium. There are many traditional cryptographic techniques which were used previously. The physical layer security used for ensuring secure wireless communications apart from the cryptographic techniques, which is achieved after proper understanding of the nature wireless channels. Classical information theoretic secrecy is one of the metrics followed, in which, we assume that there is no(zero) leaked information at the eavesdropper which means the information decoding probability at the eavesdropper is '0'. But, practically achieving classical information theoretic secrecy is not possible. So, this project deals with partial secrecy. The partial secrecy of a system is measured in terms of equivocation, which gives the information of the level at which the eavesdropper (active) is confused. It means that in partial secrecy, there is information leakage but the eavesdropper cannot exactly decode the original message. The new secrecy metrics used GSOP (generalized secrecy outage probability), AFE (average fractional equivocation) and AILR (average information leakage rate) altogether provides more comprehensive and in-depth understanding of the secrecy performance over the fading channels.

Mean-Field Artificial Noise Assistance and Uplink Power Control in Covert IoT Systems

In this paper, we study a covert Internet of Things (IoT) system. Compared with conventional IoT systems that apply cryptography and information-theoretic secrecy approaches to secure the transmission, our considered IoT system adopts the covertness technique and intends to hide the legitimate transmission from the observant adversaries. In the IoT system, the IoT devices randomly transmit the collected data to their associated IoT gateways (GWs). In the meantime, the adversaries attempt to detect the existence of legitimate transmission based on their received signal power and launch hostile attacks accordingly. To avoid being detected by the adversaries, the IoT system applies uplink power control to achieve covert legitimate transmission. Moreover, to distort the observation of the adversaries so as to mislead their decisions, we propose an artificial noise (AN)-assisted covert communication design, where the AN is transmitted by in-band full-duplex (IBFD) IoT GWs as a jamming operation. We formulate a Stackelberg game to study the interaction between the adversaries and the legitimate entities including the IoT GWs and IoT devices, where the legitimate entities, as the leaders, decide on the powers of legitimate and AN transmissions at the upper level and the adversaries, as the followers, aim to minimize their detection errors at the lower level. Thereafter, considering the large scale of IoT system, we further cast the Stackelberg game into a mean-field Stackelberg game and incorporate the stochastic geometry and statistical channel model to capture the location heterogeneity and channel dynamics among and of the system entities, respectively. In the performance evaluation, we verify the practicability of the mean-field Stackelberg game. Moreover, we demonstrate the effectiveness of AN in improving the transmission covertness.

Network Information Theoretic Security With Omnipresent Eavesdropping

Shannon showed that to achieve perfect secrecy in point-to-point communication, the message rate cannot exceed the shared secret key rate giving rise to the simple one-time pad encryption scheme. In this paper, we extend this work from point-to-point to networks. We consider a connected network with pairwise communication between the nodes and assume that each node is provided with a certain amount of secret bits before communication commences. An eavesdropper with unlimited computing power has access to all communication and can hack a subset of the nodes not known to the rest of the nodes. We investigate the limits on information-theoretic secure communication with end-to-end encryption for this network. We establish a tradeoff between the secure channel rate (for a node pair) and the secure network rate (sum over all node pair rates) and show that information-theoretic secrecy can be achieved asymptotically if and only if the sum rate of any subset of unhacked channels does not exceed the shared unhacked-secret-bit rate of these channels. We also propose a practical scheme that achieves a good balance of network and channel rates with information-theoretic secrecy guarantee. This work has a wide range of potential applications for which strong secrecy is desired, such as cyber-physical systems, distributed-control systems, and ad-hoc networks.

Secrecy Performance of Eigendecomposition-Based FTN Signaling and NOFDM in Quasi-Static Fading Channels

In this paper, we investigate the information-theoretic secrecy performance of recent precoded faster-than-Nyquist signaling (FTN) with the aid of optimal power allocation in eigenspace. More specifically, the secrecy rate and secrecy outage probability of a fading wiretap channel, which was derived for classical Nyquist-based orthogonal signaling transmission, is extended to those of our eigendecompsition-based FTN (E-FTN) signaling for a quasi-static frequency-flat Rayleigh fading channel. Our performance results demonstrate that the proposed E-FTN signaling scheme exhibits improvements in secrecy rate and secrecy outage probability over conventional Nyquist-based and FTN signaling transmission, assuming employment of a root-raised cosine filter. We also show that the same benefits as those of single-carrier E-FTN signaling are attainable by its non-orthogonal multicarrier counterpart, where subcarrier spacing is set lower than that of orthogonal frequency-division multiplexing.

Learning end-to-end codes for the BPSK-constrained Gaussian wiretap channel

Finite-length codes are learned for the Gaussian wiretap channel in an end-to-end manner assuming that the communication parties are equipped with deep neural networks (DNNs), and communicate through binary phase-shift keying (BPSK) modulation scheme. The goal is to find codes via DNNs which allow a pair of transmitter and receiver to communicate reliably and securely in the presence of an adversary aiming at decoding the secret messages. Following the information-theoretic secrecy principles, the security is evaluated in terms of mutual information utilizing a deep learning tool called MINE (mutual information neural estimation). System performance is evaluated for different DNN architectures, designed based on the existing secure coding schemes, at the transmitter. Numerical results demonstrate that the legitimate parties can indeed establish a secure transmission in this setting as the learned codes achieve points on almost the boundary of the equivocation region.

Secrecy Optimization for Diffusion-Based Molecular Timing Channels

Security in the context of molecular communication systems is an important design aspect that has not attracted much attention till date. This letter analyzes the information-theoretic secrecy of diffusive molecular timing channels when the distance of the eavesdropper is assumed to be random and uniformly distributed. Using an existing upper bound on the timing channel capacity, we calculate the optimal secrecy rate and optimal transmission rate for Bob which would help in achieving an improved secrecy throughput performance. Based on this optimal rate, we calculate the maximum achievable throughput. We then use this formulation to minimize the generalized secrecy outage probability (GSOP) by simultaneously maximizing the average fractional equivocation and minimizing the average information leakage rate. The numerical results show that while choosing the system parameters, there is always a trade-off between different performance metrics like GSOP, average fractional equivocation, and average information leakage rate. The proposed secrecy optimization provides a robust understanding of the physical layer secrecy at the molecular level, enabling the design of secure molecular communication systems.

Secrecy by Design With Applications to Privacy and Compression

Secrecy by design is examined as an approach to information-theoretic secrecy. The main idea behind this approach is to design an information processing system from the ground up to be perfectly secure with respect to an explicit secrecy constraint. The principal technical contributions are decomposition bounds that allow the representation of a random variable <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$X$ </tex-math></inline-formula> as a deterministic function of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$({S},{Z})$ </tex-math></inline-formula> , where <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$S$ </tex-math></inline-formula> is a given fixed random variable and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$Z$ </tex-math></inline-formula> is constructed to be independent of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$S$ </tex-math></inline-formula> . Using the problems of privacy and lossless compression as examples, the utility cost of applying secrecy by design is investigated. Privacy is studied in the setting of the privacy funnel function previously introduced in the literature and new bounds for the regime of zero information leakage are derived. For the problem of lossless compression, it is shown that strong information-theoretic guarantees can be achieved using a reduced secret key size and a quantifiable penalty on the compression rate. The fundamental limits for both problems are characterized with matching lower and upper bounds when the secret <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$S$ </tex-math></inline-formula> is a deterministic function of the information source <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$X$ </tex-math></inline-formula> .

Joint Information-Theoretic Secrecy and Covert Communication in the Presence of an Untrusted User and Warden

In this article, we investigate joint information-theoretic secrecy and covert communication in a single-input–multioutput (SIMO) system where a transmitter (Alice) is communicating with two legitimate users (Bob and Carol). We consider that an untrusted user and a warden node are also present in the network attempting to attack the secure and covert communications to Bob and Carol, respectively. Specifically, Bob requires secure communications such that his messages from Alice are not decoded by the untrusted user, while Carol requires covert communications such that her messages from Alice are not detected by the warden. To do so, we consider that Alice transmits Carol’s messages during selected time slots to hide them from the warden while also transmitting Bob’s messages in each time slot contentiously. We formulate an optimization problem with the aim of maximizing the average rate subject to a covert communication requirement and a secure communications constraint. Since the proposed optimization problem is nonconvex, we utilize successive convex approximation to obtain a tractable solution. Moreover, we extend our proposed system model to multiple antenna Alice scenario and find beamforming vectors so that the average sum rate is maximized. Furthermore, we consider practical assumptions that Alice has imperfect knowledge of the warden’s location and imperfect channel state information (CSI) of Bob and Carol. Our numerical examples highlight that the imperfect CSI at Carol has a more detrimental impact on the average rate compared to imperfect CSI at Bob.

Secrecy Capacity of FBMC-OQAM Modulation Over Frequency Selective Channel

This letter studies the information-theoretic secrecy capacity of an Offset-QAM-based filterbank multicarrier (FBMC-OQAM) communication over a wiretap frequency selective channel. The secrecy capacity is formulated as an optimization problem which has a closed-form solution in the high signal-to-noise ratio (SNR) regime. Two of the most common equalization strategies in FBMC-OQAM are considered, namely, single-tap and multi-tap equalization. For the sake of comparison, we also consider the secrecy capacity of a generic modulation and a cyclic prefix-orthogonal frequency division multiplexing (CP-OFDM) modulation. As a result, we find that FBMC-OQAM is particularly competitive for medium-to-long burst transmissions.

Homomorphic encryption of linear optics quantum computation on almost arbitrary states of light with asymptotically perfect security

Future quantum computers are likely to be expensive and affordable outright by few, motivating client/server models for outsourced computation. However, the applications for quantum computing will often involve sensitive data, and the client would like to keep her data secret, both from eavesdroppers and the server itself. Homomorphic encryption is an approach for encrypted, outsourced quantum computation, where the client's data remains secret, even during execution of the computation. We present a scheme for the homomorphic encryption of arbitrary quantum states of light with no more than a fixed number of photons, under the evolution of both passive and adaptive linear optics, the latter of which is universal for quantum computation. The scheme uses random coherent displacements in phase-space to obfuscate client data. In the limit of large coherent displacements, the protocol exhibits asymptotically perfect information-theoretic secrecy. The experimental requirements are modest, and easily implementable using present-day technology.

Secrecy sum-rate of multi-user MISO visible light communication systems with confidential messages

This paper studies the information theoretic secrecy sum-rate for multi-user multiple-input single-output (MU-MISO) visible light communication (VLC) systems with confidential messages. The well-known zero-forcing (ZF) precoding technique is employed to ensure confidentiality among legitimate users and, at the same time, to prevent eavesdropper(s) from obtaining any information. Different from radio frequency (RF) counterpart where the average input power constraint is usually imposed on the derivation of channel capacity, the input data signal of VLC systems is amplitude constrained, leading to a peak input power constraint. The amplitude constraint gives rise to the complexity in obtaining an analytical expression for the capacity. In this paper, we analytically investigate a novel bound on the secrecy sum-rate of all legitimate users in MU-MISO VLC systems, which is valid in high signal-to-noise ratio (SNR) regime. The secrecy sum-rate performance is then derived for two scenarios: known and unknown eavesdropper's channel state information (CSI) at the transmitter.

SCBF: Exploiting a Collision for Authentication in Backscatter Networks

Backscatter networks are widely applied in real world such as inventory management, RFID-enabled passport, and access control. The security issues rapidly grow in its importance with the widespread uses. Especially, if the access control application identifies a user using a message from a backscatter device, the message can be used for tracking or replay attacks. However, most of the existing security protocols depending on cryptosystems cannot be applied into the backscatter networks due to the minimalist design of backscatter devices. In order to alleviate the security menaces, we propose a novel concept of authentication scheme for backscatter networks. Our scheme uses an unpredictable collision by applying our own data structure called Shifted Counting Bloom Filter (SCBF) . Based on the SCBF, the scheme can reduce the overhead of backscatter devices required for security. Our performance evaluation shows the information-theoretic secrecy and the reliability of our scheme.

Directional Modulation Via Symbol-Level Precoding: A Way to Enhance Security

Wireless communication provides a wide coverage at the cost of exposing information to unintended users. As an information-theoretic paradigm, secrecy rate derives bounds for secure transmission when the channel to the eavesdropper is known. However, such bounds are shown to be restrictive in practice and may require exploitation of specialized coding schemes. In this paper, we employ the concept of directional modulation and follow a signal processing approach to enhance the security of multi-user MIMO communication systems when a multi-antenna eavesdropper is present. Enhancing the security is accomplished by increasing the symbol error rate at the eavesdropper. Unlike the information-theoretic secrecy rate paradigm, we assume that the legitimate transmitter is not aware of its channel to the eavesdropper, which is a more realistic assumption. We examine the applicability of MIMO receiving algorithms at the eavesdropper. Using the channel knowledge and the intended symbols for the users, we design security enhancing symbol-level precoders for different transmitter and eavesdropper antenna configurations. We transform each design problem to a linearly constrained quadratic program and propose two solutions, namely the iterative algorithm and one based on non-negative least squares, at each scenario for a computationally-efficient modulation. Simulation results verify the analysis and show that the designed precoders outperform the benchmark scheme in terms of both power efficiency and security enhancement.

The Henchman Problem: Measuring Secrecy by the Minimum Distortion in a List

We introduce a new measure of information-theoretic secrecy based on rate-distortion theory and study it in the context of the Shannon cipher system. Whereas rate-distortion theory is traditionally concerned with a single reconstruction sequence, in this paper, we suppose that an eavesdropper produces a list of $2^{nR_{\sf L}}$ reconstruction sequences and measure secrecy by the minimum distortion over the entire list. We show that this setting is equivalent to one in which an eavesdropper must reconstruct a single sequence, but also receives side information about the source sequence and public message from a rate-limited henchman (a helper for an adversary). We characterize the optimal tradeoff of secret key rate, list rate, and eavesdropper distortion. The solution hinges on a problem of independent interest: lossy compression of a codeword uniformly drawn from a random codebook. We also characterize the solution to the lossy communication version of the problem in which distortion is allowed at the legitimate receiver. The analysis in both the settings is greatly aided by a recent technique for proving source coding results with the use of a likelihood encoder.

Optimal secrecy capacity-delay tradeoff in large-scale mobile ad hoc networks

In this paper, we investigate the impact of information-theoretic secrecy constraint on the capacity and delay of mobile ad hoc networks (MANETs) with mobile legitimate nodes and static eavesdroppe...

Optimal Secrecy Capacity-Delay Tradeoff in Large-Scale Mobile Ad Hoc Networks

In this paper, we investigate the impact of information-theoretic secrecy constraint on the capacity and delay of mobile ad hoc networks (MANETs) with mobile legitimate nodes and static eavesdroppers whose location and channel state information (CSI) are both unknown. We assume $n$ legitimate nodes move according to the fast i.i.d. mobility pattern and each desires to communicate with one randomly selected destination node. There are also $n^{\nu}$ static eavesdroppers located uniformly in the network and we assume the number of eavesdroppers is much larger than that of legitimate nodes, i.e., $\nu>1$ . We propose a novel simple secure communication model, i.e., the secure protocol model, and prove its equivalence to the widely accepted secure physical model under a few technical assumptions. Based on the proposed model, a framework of analyzing the secrecy capacity and delay in MANETs is established. Given a delay constraint $D$ , we find that the optimal secrecy throughput capacity is $\widetilde{\Theta}(W((D/n))^{(2/3)})$ , where $W$ is the data rate of each link. We observe that: 1) the capacity-delay tradeoff is independent of the number of eavesdroppers, which indicates that adding more eavesdroppers will not degenerate the performance of the legitimate network as long as $\nu>1$ ; 2) the capacity-delay tradeoff of our paper outperforms the previous result $\Theta((1/n\psi_{e}))$ in , where $\psi_{e}=n^{\nu-1}=\omega(1)$ is the density of the eavesdroppers. Throughout this paper, for functions $f(n)$ and $g(n)$ , we denote $f(n)=o(g(n))$ if $\lim_{n\rightarrow\infty}(f(n)/g(n))=0$ ; $f(n)=\omega(g(n))$ if $g(n)=o(f(n))$ ; $f(n)=O(g(n))$ if there is a positive constant $c$ such that $f(n)\leq cg(n)$ for sufficiently large $n$ ; $f(n)=\Omega(g(n))$ if $g(n)=O(f(n))$ ; $f(n)=\Theta(g(n))$ if both $f(n)=O(g(n))$ and $f(n)=\Omega(g(n))$ hold. Besides, the order notation $\widetilde{\Theta}$ omits the polylogarithmic factors for better readability.

Analysis of One-Time Random Projections for Privacy Preserving Compressed Sensing

In this paper, the security of the compressed sensing (CS) framework as a form of data confidentiality is analyzed. Two important properties of one-time random linear measurements acquired using a Gaussian independent identically distributed matrix are outlined: 1) the measurements reveal only the energy of the sensed signal and 2) only the energy of the measurements leaks information about the signal. An important consequence of the above facts is that CS provides information theoretic secrecy in a particular setting. Namely, a simple strategy based on the normalization of the Gaussian measurements achieves, at least in theory, perfect secrecy, enabling the use of CS as an additional security layer in privacy preserving applications. In the generic setting in which CS does not provide information theoretic secrecy, two alternative security notions linked to the difficulty of estimating the energy of the signal and distinguishing equal-energy signals are introduced. Useful bounds on the mean square error of any possible estimator and the probability of error of any possible detector are provided and compared with the simulations. The results indicate that CS is in general not secure according to cryptographic standards, but may provide a useful built-in data obfuscation layer.

Polar Coding for the General Wiretap Channel With Extensions to Multiuser Scenarios

Information-theoretic work for wiretap channels is mostly based on random coding schemes. Designing practical coding schemes to achieve information-theoretic secrecy is an important problem. By applying two recently developed techniques for polar codes, namely, universal polar coding and polar coding for asymmetric channels, we propose a polar coding scheme to achieve the secrecy capacity of the general wiretap channel. We then apply this coding scheme to achieve the best-known inner bounds for the multiple access wiretap channel (MAC-WTC), and the broadcast and interference channels with confidential messages (BC-CM and IC-CM).

To avoid or not to avoid CSI leakage in physical layer secret communication systems

Physical layer secrecy has attracted much attention in recent years due to its ability to ensure communication secrecy with the use of channel coding and signal processing techniques (and without the explicit use of secret keys) in the physical layer. It serves as a promising technique for highly dynamic or ad hoc systems such as device-to-device and machine-type communication systems. However, the achievable secrecy performance depends highly on the level of CSI at the transmitter, the receiver, and the eavesdropper. In this article, we discuss how different levels of CSI resulting from conventional and unconventional ways of performing training and channel feedback may affect the confidentiality in terms of the information-theoretic (perfect) secrecy rate. The conventional approach refers to the emission of pilot signals from the transmitter and explicit channel feedback from the receiver. This approach is backward compatible with existing systems and allows the receiver to obtain accurate knowledge of the CSI, but may suffer from CSI leakage toward the eavesdropper. Unconventional approaches capitalize on reverse training to prevent CSI leakage and are shown to achieve significant improvements over conventional schemes in certain cases. For example, in a system with four transmit antennas and a single antenna at both the receiver and the eavesdropper, a secrecy rate gain of approximately 0.8 b/channel use at transmit SNR of 16 dB is observed over the full CSI case by providing CSI only to the transmitter (but not the receiver and the eavesdropper).