In this paper, we propose a physical layer secret key (PLSK) generation scheme for secure encrypted transmissions in orbital angular momentum (OAM) communication systems which improves the secret key capacity via taking advantage of OAM orthogonal modes. Based on the line-of-sight (LoS) quasi-static channel conditions in OAM systems, we propose a mode-based active defense phase in the PLSK scheme to invalidate keys generated by an eavesdropper when it is extremely close to the legitimate user. Our simulation results highlight that the key information generated by the eavesdropper is almost zero in the case of highly correlated legitimate and eavesdropping channels under LoS conditions. In addition, our proposed OAM PLSK scheme achieves a higher key generation rate (KGR) than existing works since mode-based active defense can disrupt the process of PLSK by the eavesdropper.
In this paper, we propose a physical layer secret key (PLSK) generation scheme for secure encrypted transmissions in orbital angular momentum (OAM) communication systems which improves the secret key capacity via taking advantage of OAM orthogonal modes. Based on the line-of-sight (LoS) quasi-static channel conditions in OAM systems, we propose a mode-based active defense phase in the PLSK scheme to invalidate keys generated by an eavesdropper when it is extremely close to the legitimate user. Our simulation results highlight that the key information generated by the eavesdropper is almost zero in the case of highly correlated legitimate and eavesdropping channels under LoS conditions. In addition, our proposed OAM PLSK scheme achieves a higher key generation rate (KGR) than existing works since mode-based active defense can disrupt the process of PLSK by the eavesdropper.
In this paper, we propose a novel physical-layer key generation (PKG) scheme for orthogonal frequency division multiplexing-orbital angular momentum (OFDM-OAM) systems to significantly enhance the confidentiality capacity (CC). In the proposed scheme, we first establish the OAM channel model under uniform circular array (UCA) misalignment in the line-of-sight (LoS) channel. Facing the risk of information leakage during key negotiation, we couple key generation with the OFDM communication process. Then, we analyze the CC of the OFDM-OAM system and derive its closed-form expression. Simulation results illustrate that the proposed OFDM-OAM PKG scheme has achieved high CC compared with existing works. In addition, as the offset angle of the eavesdropper’s UCA increases, the CC increases, and the bit error rate (BER) of the eavesdropper tends to be 0.5.
Different from reflecting-only metasurfaces, intelligent omni-surfaces (IOSs) are capable of both refracting and reflecting the received signals, providing a new technical solution to overcome coverage limitations. In this paper, we propose a physical layer secret key (PLSK) generation scheme in IOS-assisted communication systems for the first time. This scheme enhances the key generation rate (KGR) for legitimate users on both sides of the IOS. A selective optimization stage, based on proximal policy optimization (PPO) is designed to configure different refraction and reflection coefficients to improve secrecy performance. In addition, IOS random elements are allocated as artificial random sources to invoke variations of the legitimate channel, to weaken the capability of the eavesdropper to acquire the key. Simulation results demonstrate that the proposed scheme ensures the randomness of the PLSK while achieving a higher KGR than existing works under quasi-static conditions.
In this paper, we evaluate the achievable rates of the physical layer security (PLS)-based secret key generation (SKG) in a line-of-sight (LoS) channel, which occurs with a high probability in unmanned aerial vehicle (UAV) communications. SKG is a promising technique for lightweight scalable key distribution, and, despite the mature theory of PLS, this technique remains to be seen in practical applications. Thus, modelling realistic scenarios is of particular interest. One of the reasons why SKG has not been used in practice is due to the deterministic properties of LoS channels. To overcome this problem, in this paper we propose the rotation of the device antennas as an entropy source, reflected by the channel phases, from which the keys are derived. Simulation results show that by utilizing rotation in LoS scenarios, a number of secret bits can be generated, also given the presence of an eavesdropper. It is also shown that by controlling the transmit power we can maximize the conditional mutual information.
Orbital angular momentum (OAM) provides an additional degree of freedom for information transmission. However, wireless transmissions with OAM are challenged by secrecy issues since the OAM modes can be observed over a wide range along the beam axis, and it allows that the eavesdroppers intercept the information bits encoded on the OAM modes. In this letter, targeting against unintended receivers, we propose a secure range-dependent transmission scheme with OAM radio beams generated by the frequency diverse array (FDA). Specifically, we consider a line-of-sight communication link overheard by an unknown eavesdropper. The transmitter employs FDA of antennas to generate range-dependent OAM radio beams and target at the legitimate receiver, in which the confidential information is encoded on the OAM modes. The eavesdropper outside the target region observes distorted OAM modes and thus is unable to recover the secret messages. The proposed scheme enhances the security of OAM mode modulation and achieves higher energy efficiency compared to the conventional secure transmission schemes with artificial noise.
As a new way to enhance wireless communication security, secret key generation based on physical layer channel characteristics has emerged. In this paper, we propose a novel secret key generation algorithm based on wireless channel characteristics for orthogonal frequency division multiplexing (OFDM) communication systems. The mean quantization algorithm is applied to quantize the real part and imaginary part of OFDM subcarriers, respectively, which can significantly increase the length of the generated secret key in the OFDM system. To reduce the consistency between the secret keys generated by the eavesdropper and the legitimate communication nodes, a processing method by taking the subcarrier phase as initialization of a scrambling code and scrambling the quantized result is proposed. The simulation and test results show that compared with the existing research, the proposed algorithm can improve the key generation rate (KGR), reduce the key mismatch rate (KMR) and complexity, maintain high randomness, and disturb the eavesdroppers.
Unmanned aerial vehicle (UAV) will be an essential carrier for future wireless communications due to its flexible deployment and low cost. As such, the information security of UAV communications is of paramount concern. In this paper, a novel physical layer secret key generation scheme is proposed for air-to-ground (A2G) UAV multiple-input-multiple-output (MIMO) communications, which is applicable in frequency division duplex (FDD) systems. In UAV communications, line-of-sight (LoS) propagation is a distinctive feature, which significantly weakens the performance of channel state information (CSI) based keys. Therefore, a novel channel parameter, three-dimension (3D) spatial angle, is employed to combat against a novel active eavesdropping method, which is termed as Environment Reconstruction based Attack for SEcret keys (ERASE). Compared to the existing plane-angle-based method, our scheme can efficiently utilize spatial resources and provide a higher key generation rate (KGR). The advantages of the proposed scheme are shown through both theoretical analysis and simulations.