In this paper, we propose a novel physical-layer secret key generation (SKG) scheme, which is based on reduced random pilot selection at a legitimate transmitter and channel interpolation at a legitimate receiver. As a result, the proposed scheme is capable of reducing pilot overhead and increasing secret key capacity (SKC) while suppressing information leakage to an eavesdropper in a correlated eavesdropping channel. More specifically, a subset of full pilot sequence is activated based on the legitimate channels at the legitimate transmitter, and the full channel coefficients are estimated from the received pilot symbol subset at the legitimate receiver with the aid of our channel interpolation. Additionally, despite the non-reciprocal channel due to the presence of a Doppler shift and an additive noise, our scheme achieves high SKG reliability in comparison to that without our reduced pilot selection or channel interpolation. We also derive the theoretical SKC for the proposed scheme. Our simulation results demonstrate that the proposed SKG scheme exhibits a higher performance in terms of both the SKC and key disagreement ratio.
In this paper, we propose a novel physical-layer secret key generation (SKG) scheme, which is based on reduced random pilot selection at a legitimate transmitter and channel interpolation at a legitimate receiver. As a result, the proposed scheme is capable of reducing pilot overhead and increasing secret key capacity (SKC) while suppressing information leakage to an eavesdropper in a correlated eavesdropping channel. More specifically, a subset of full pilot sequence is activated based on the legitimate channels at the legitimate transmitter, and the full channel coefficients are estimated from the received pilot symbol subset at the legitimate receiver with the aid of our channel interpolation. Additionally, despite the non-reciprocal channel due to the presence of a Doppler shift and an additive noise, our scheme achieves high SKG reliability in comparison to that without our reduced pilot selection or channel interpolation. We also derive the theoretical SKC for the proposed scheme. Our simulation results demonstrate that the proposed SKG scheme exhibits a higher performance in terms of both the SKC and key disagreement ratio.
In this paper, we propose a novel physical-layer secret key generation (SKG), which randomly activates a pilot sequence during the channel probing phase. Each legitimate user interpolates the received signals to recover the full channel state information (CSI). Due to the random reduction of the pilot sequence, the proposed scheme can degrade the eavesdropping performance regardless of the correlation between legitimate users and eavesdroppers, thereby improving the secret key capacity (SKC). Furthermore, low power consumption during the channel probing phase can be achieved. Our simulation results demonstrate that the proposed scheme exhibits superior performance in the presence of eavesdroppers.
In this paper, we investigate the physical layer key generation scheme in most realistic scenarios where the correlation between the legitimate channel and the eavesdropping channel is considered. To degrade the correlation and improve the key generation capacity, a physical layer key generation scheme through scrambling the correlated eavesdropping channel is proposed. Firstly, the artificial noise is sent superimposed over pilots from the legitimate transmitter to confuse the eavesdropper. The artificial noise precoding matrix is randomly selected from decomposed unitary matrices orthogonal to the legitimate channel resulting in having no effect on legitimate channel. Then, the vector quantization algorithm and the winnow algorithm are respectively applied to quantize the channel characteristic and negotiate the generated random sequences to generate the final key. To further support the performance, we next present a power optimization scheme allocated to sending the artificial noise to maximize the generated key capacity under the total transmission power constraint. Finally, simulation results are presented to validate the effectiveness of our proposed scheme.
Physical layer secret key generation exploits the reciprocal channel randomness for key generation and has proven to be an effective addition security layer in wireless communications. However, static or scarcely random channels require artificially induced dynamics to improve the secrecy performance, e.g., using intelligent reflecting surface (IRS). One key challenge is that the induced random phase from IRS is also reflected in the direction to eavesdroppers (Eve). This leakage enables Eve nodes to estimate the legitimate channels and secret key via a globally known pilot sequence. To mitigate the secret key leakage issue, we propose to exploit random matrix theory to inform the design of a new physical layer secret key generation (PL-SKG) algorithm. We prove that, when sending appropriate random Gaussian matrices, the singular values of Alice's and Bob's received signals follow a similar probability distribution. Leveraging these common singular values, we propose a random Gaussian matrix based PL-SKG (RGM PL-SKG), which avoids the usages of the globally known pilot and thereby prevents the aforementioned leakage issue. Our results show the following: (i) high noise resistance which leads to superior secret key rate (SKR) improvement (up to 300%) in low SNR regime, and (ii) general improved SKR performance against multiple colluded Eves. We believe our combination of random matrix theory and PL-SKG shows a new paradigm to secure the wireless communication channels.
Recently, shared secret key generation from wireless channel characteristics has attracted a lot of attention due to its low computational overhead. However, in a static environment, the secret key rate is relatively lower due to the lack of channel time-variation. In this paper, we propose a lightweight and efficient PLKG scheme for static channels. Different from current schemes, in the proposed scheme, the transmitter attaches the information of the secret key into the downlink pilot signals to the legitimate receiver by the proposed secret precoding. At the receiving end, the legitimate receiver can directly observe the correct information of secret key from the public downlink pilot signals, while keeping perfect secrecy of the generated key against eavesdroppers. The key principle lies in that the information of the secret key is coded in the index of the non-activated MIMO (multiple-input-multiple-output) sub-channel. Consequently, only the legitimate receiver can accurately observe the value of the key information. For any other eavesdroppers who suffer an independent channel from the legitimate transmitter and receiver, it is proven that she cannot observe any key information from her received signals. Therefore, the key rate can be improved for the static channels by increasing the symbol rate of the pilot signals. Simulations are conducted to validate the effectiveness of the proposed scheme.
This paper presents a random pilot full-duplex (FD) secret key generation scheme designed to enhance security in static wireless environments. In these environments, where inherent channel randomness is limited, efficiently extracting secret keys poses a significant challenge. The proposed scheme leverages the benefits of both FD operation and random pilot transmission to overcome this limitation and enhance the physical layer security. In this scheme, one of the FD nodes transmits random pilot signals, unknown to the eavesdropper, during the channel probing phase to artificially increase the shared randomness between the legitimate communicating nodes. By considering correlated eavesdropping, we derive the lower and upper bounds for the achievable secret key rate (SKR). The results reveal that the proposed FD scheme outperforms the HD scheme even in the presence of residual SI. Furthermore, the secret key rate can be improved by better SIC channel estimation and lower eavesdropper channel correlation.
Physical layer (PHY) secret key generation (SKG) has been widely studied as a promising approach to achieving One-Time-Pad security. The improvement of SKG rate is quite a huge challenge, especially in scenarios with untrusted internal helpers or eavesdroppers that aim to wiretap the negotiated secret keys between legitimate parties. In this paper, we propose a token-based SKG scheme to deal with the problem of information leakage with internal eavesdropping attacks. The basic idea is to cover random pilots with protective tokens to confuse eavesdroppers. Three scenarios including passive external eavesdropping, active internal eavesdropping with a reconfigurable intelligent surface (RIS)-assisted untrusted helper, and active internal eavesdropping with an untrusted relay are considered and analyzed to evaluate the performance of the proposed anti-eavesdropping scheme. Theoretical analysis shows that the proposed token-based SKG scheme can perfectly secure the key negotiation, achieving zero information leakage even in the untrusted relaying scenario without a direct link between Alice and Bob. Moreover, closed-form expressions for secret key capacity (SKC) are obtained. Finally, numerical results indicate that the proposed scheme outperforms the state-of-the-art methods. Using a token-generation mapping function with greater diversity in amplitude and phase, our approach achieves enhanced SKC performance across various scenarios, including those with a passive eavesdropper, a RIS-assisted untrusted helper, and an untrusted relay.