Scrambling is a way of enhancing physical layer security presented in many papers. However, few of these papers have mentioned the scrambling effect on the polar coding secrecy. In this letter, we introduce a new scrambling module combined with a polar coding system, in which pre-assigned key is unnecessary. The presented scrambling module combines linear and nonlinear structure. The presented linear structure increases the branch number in a low-complexity way to enhance algorithm diffusion power, and the nonlinear part can resist the differential attack and reduces the mutual information between its input and output. With the proposed module, the bit channels, which are good for Bob and Eve, can also be applied to transmit secret message, making transmission rate of the secret massage configurable. Simulation results show that our method can guarantee the secrecy transmission between Alice and Bob.
Scrambling is a way of enhancing physical layer security presented in many papers. However, few of these papers have mentioned the scrambling effect on the polar coding secrecy. In this letter, we introduce a new scrambling module combined with a polar coding system, in which pre-assigned key is unnecessary. The presented scrambling module combines linear and nonlinear structure. The presented linear structure increases the branch number in a low-complexity way to enhance algorithm diffusion power, and the nonlinear part can resist the differential attack and reduces the mutual information between its input and output. With the proposed module, the bit channels, which are good for Bob and Eve, can also be applied to transmit secret message, making transmission rate of the secret massage configurable. Simulation results show that our method can guarantee the secrecy transmission between Alice and Bob.
In this study, by exploiting the properties of finite‐length polar codes, the authors introduce a physical layer encryption scheme to make secure (from a computational security perspective) and efficient communication between a sender (Alice) and a legitimate receiver (Bob) against both active and passive attacks, simultaneously. To prevent active attacks, two techniques are considered: (i) a novel method is introduced to keep the generator matrix of polar code secret from an active attacker (Oscar); (ii) a proper joint polar encoding/encryption algorithm based on the hidden generator matrix is introduced. Two additional strategies are considered against passive attacks: (i) a new method is introduced to partition the bit‐channels into good and bad bit‐channels and then the scrambled information bits are transmitted over those bit‐channels that are good for Bob but bad for a passive attacker (Eve); (ii) the secret key cryptography is implemented at the physical layer, such that Eve cannot decode the eavesdropped data without the knowledge of the secret key shared between the authorised parties. Besides, this study discusses efficiency analysis results consisting key size, error performance and computational complexity of the proposed scheme.
Physical layer security (PLS) enables secure communication which is independent of cryptography. It generally requires the legitimate channel being advantageous, otherwise, relaying techniques can be adopted to enhance the legitimate transmission and/or suppress the wiretap one. However, untrusted relays become new threatens since unknown passive eavesdroppers may approach either the transmitter or the receiver to wiretap the secure messages. Regarding the threatens in this setup, we propose a nonlinear transmit and relaying approach to protect the secure messages during the overall transmission. The essential idea is that Alice transmits a nonlinear transform of the original secure signal and the relays collaboratively invert the nonlinear transform at Alice when forwarding it to Bob. By carefully designing the layout of the relays, only a confined region where Bob locates is accessible to the non-distortion version of the original secure signal, and there is no secure signal leakage nearby Alice or the relays. Specifically, the proposed scheme consists of two phases. In the first one, a well-chosen nonlinear transform is applied to the secure signal of Alice, and she then broadcasts the transformed signal to both the relays and the eavesdropper. Each relay determines its forwarding approach by using either the Taylor series or the Lagrange inversion theorem on the nonlinear function of Alice to facilitate the perfect recovery of the original secure signal for Bob. In the second phase, the relays process the received signals using the well-designed forwarding approach and then cooperatively send them to Bob. The forwarding signals are aggregated at Bob and the original secure signal can be recovered directly without any further complicated equalization. We therefore define the region with this property by the secure-information-accessible region, and then provide the secrecy suggestions of laying the relays to shrink it. In contrast, the eavesdropper cannot get any useful secure information from either the first phase or the second one if it locates out of this region. Finally, we analyze both the bit error rate and the secrecy rate, and compare them with the existing secrecy methods. Numerical results validate the proposed nonlinear secrecy approach.
The advent of fifth-generation (5G) technology has ushered in a new era of connectivity, promising unprecedented data rates and ultra-reliable low-latency communication. As the demand for high-speed and secure communication continues to surge, there is a critical need for robust communication systems to increase wireless networks' security level. In this context, this paper investigates secure communication techniques, specifically focusing on utilizing the hash function as an authentication mechanism and the presence of polar codes. The integration of polar codes within the communication framework and their effectiveness are examined to enhance error correction capabilities by ensuring the integrity of transmitted data. Furthermore, the transmissions between Alice, Bob, and Eve are evaluated in terms of authentication rate, secrecy rate, and secrecy capacity in determining the effect of the hash function, the presence of channel pre-coding algorithm, and various codeword lengths. This paper also investigates the impact of different codeword values on the overall system performance, shedding light on the advantages of tailoring these parameters to the unique requirements of 5G networks. The results found that the performance of secure communication with the presence of polar codes is better than that of transmission without polar codes. The secrecy rate is reduced to below 10−4after the transmission reaches 7 dB, Bob's authentication rate remains high, almost reaching 1.
Suppose Alice wishes to send messages to Bob through a communication channel C_1, but her transmissions also reach an eavesdropper Eve through another channel C_2. The goal is to design a coding scheme that makes it possible for Alice to communicate both reliably and securely. Reliability is measured in terms of Bob's probability of error in recovering the message, while security is measured in terms of Eve's equivocation ratio. Wyner showed that the situation is characterized by a single constant C_s, called the secrecy capacity, which has the following meaning: for all ε>0, there exist coding schemes of rate R≥Cs−ε that asymptotically achieve both the reliability and the security objectives. However, his proof of this result is based upon a nonconstructive random-coding argument. To date, despite a considerable research effort, the only case where we know how to construct coding schemes that achieve secrecy capacity is when Eve's channel C_2 is an erasure channel, or a combinatorial variation thereof. Polar codes were recently invented by Arikan; they approach the capacity of symmetric binary-input discrete memoryless channels with low encoding and decoding complexity. Herein, we use polar codes to construct a coding scheme that achieves the secrecy capacity for a wide range of wiretap channels. Our construction works for any instantiation of the wiretap channel model, as long as both C_1 and C_2 are symmetric and binary-input, and C_2 is degraded with respect to C_1. Moreover, we show how to modify our construction in order to provide strong security, in the sense defined by Maurer, while still operating at a rate that approaches the secrecy capacity. In this case, we cannot guarantee that the reliability condition will be satisfied unless the main channel C_1 is noiseless, although we believe it can be always satisfied in practice.
A secret-key sharing strategy based on layered broadcast coding is introduced for slow fading channels. In the model considered, Alice wants to share a key with Bob while keeping the key secret from a passive eavesdropper, Eve. Both Alice-Bob and Alice-Eve channels are assumed to undergo slow fading, and perfect channel state information (CSI) is assumed to be known only at the receivers during the transmission. Layered coding facilitates adapting the reliably decoded rate at Bob to the actual channel state without CSI available at Alice. The index of a reliably decoded layer is sent back to Alice via a public and error-free channel, which is exploited by Alice and Bob to generate the secret key. In this paper, the secrecy key rate is derived. In addition, the optimal power distribution over coded layers is characterized. It is shown that layered coding can increase the secrecy key rate significantly compared with single-level coding.
In this paper, we consider a secure communication over the physical layer. The objective of the system is, at the physical layer security, the randomness of the channel and the polar coded aided artificial noise provide the security to the system without any secret key generation in higher layer encryption. Artificial noise will be injected at the last codeword of the confidential bits of polar codes in transmission block. Jamming position algorithm is used to initialize the position of artificial noise. The Bhattacharya parameter is used to select the position of jamming with regard to the reliability of the channel. The legitimate receiver has the knowledge of artificial noise and the confidential bit position, so it will eliminate the AN but Eve does not have the knowledge of jamming position so it cannot eliminate the AN. Simulation results show the performance of secrecy rate and the security gap of the system with the help of adding artificial noise at the last transmission block.