Orthogonal frequency division multiplexing (OFDM) is such a vital waveform scheme that is utilized in fifth-generation (5G) communication systems as well as the previous one. Since the usage scenarios of 5G are quite wide, the security of those systems is currently an open and critical issue. In this paper, a promising paradigm is proposed for enhancing physical layer (PHY) security in OFDM systems. Two independent secret keys are extracted by legitimate users quantizing the channel measurements. Those key sequences are exchanged via a novel artificial noise (AN) injection method which does not result in a key mismatch. Bit error rate (BER) versus signal-to-noise ratio (SNR) performance of the adversary is still low even if the malicious node has better channel than the legitimate user. After agreement upon the same key, both legitimate parties directly employ key sequence and inter-carrier interference matrix caused by the local oscillators to produce a secrecy matrix. This matrix enables secure communication by inserting it into the transmission design.
Orthogonal frequency division multiplexing (OFDM) is such a vital waveform scheme that is utilized in fifth-generation (5G) communication systems as well as the previous one. Since the usage scenarios of 5G are quite wide, the security of those systems is currently an open and critical issue. In this paper, a promising paradigm is proposed for enhancing physical layer (PHY) security in OFDM systems. Two independent secret keys are extracted by legitimate users quantizing the channel measurements. Those key sequences are exchanged via a novel artificial noise (AN) injection method which does not result in a key mismatch. Bit error rate (BER) versus signal-to-noise ratio (SNR) performance of the adversary is still low even if the malicious node has better channel than the legitimate user. After agreement upon the same key, both legitimate parties directly employ key sequence and inter-carrier interference matrix caused by the local oscillators to produce a secrecy matrix. This matrix enables secure communication by inserting it into the transmission design.
Exploiting the inherent physical properties of wireless channels to complement or enhance the traditional security mechanisms has attracted prominent attention recently. However, the existing secret key generation schemes suffer from miscellaneous extracting procedure. Many PHY-layer authentication schemes assume that the knowledge of the shared key is preknown. In this paper, we propose PHY-layer secret key generation and authentication schemes for orthogonal frequency-division multiplexing (OFDM) systems. In the secret key generation scheme, to simplify the extracting procedure, only one legitimate party is chosen to probe the channel and quantize the measurements to obtain the preliminary key. The preliminary key is masked by the channel-phase after the mapping and before equalization and distributed to the other party. The final shared key is used for the PHY-layer authentication scheme in which random signals and the shared key masked by the channel-phase are exchanged at the PHY-layer. Then, a binary hypothesis test is formulated for authentication. Simulation results show that the proposed secret key generation scheme outperforms the existing schemes. For the PHY-layer authentication scheme, it is immune to various passive and active attacks and a high successful authentication rate is acquired even at low signal-to-noise ratio region.
PHY-layer security is one of promising techniques for enhanced security and privacy protection in 5G communications. In this paper, the joint resource allocation and artificial noise (AN) design problem of multiuser wiretap orthogonal frequency-division multiplexing (OFDM) systems is investigated to improve the system secrecy rate and power efficiency, which can help to provide waveform design references for secure 5G communications. In such a multiuser wiretap OFDM system, one legitimate transmitter (Alice), multiple legitimate receivers (Bobs), and one eavesdropper (Eve) are simultaneously considered. The time-domain artificial noise is firstly involved to guarantee the target secrecy rates of multiple Bobs. Then a sum secrecy rate maximization problem with nonconvex integer nonlinear programming is formulated to jointly optimize the power, subcarrier allocation and AN design. To solve this tough problem with low computational complexity, a heuristical sub-optimal subcarrier allocation method is proposed, followed by the Lagrange dual method based joint power allocation and AN design scheme. Moreover, considering that sum secrecy rate maximization may result in unfairness for Bobs with bad channel gains, the transmit power minimization problem that ensures a target secrecy rate for each individual Bob is further addressed. An iterative algorithm is proposed to solve this power minimization problem by updating the subcarrier, power allocation and AN design alternatively. Numerical results demonstrate the effectiveness of the proposed algorithms.
Information is regarded as a resource with highest organizational value. Its confidentiality, integrity and authenticity are important for any organization. The broadcast nature of wireless medium makes communication vulnerable to security attacks such as eavesdropping, non-repudiation, denial of service and more. Hence, prior to transmission of information, a secret key is securely exchanged between sender and receiver. Conventional key generation algorithms work at the application layer. However, they suffer from computational overheads and require a reliable third party. Moreover, when system grows complex, these methods start failing considerably. To encounter these issues, a novel key exchange mechanism is proposed which works at the physical layer. The proposed method is based on the concept of self-jamming and exploits the properties of Orthogonal Frequency Division Multiplexing (OFDM). The simulation results show that the proposed scheme has a low Bit Error Rate (BER) for the receiver and high BER for the eavesdropper. It has also been shown that the number of attempts that eavesdropper has to make to guess the correct key are large, thereby decreasing its probability to decode the correct key.
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.
In physical-layer security, secret bits are extracted from wireless channels. With the assumption of channel reciprocity, the legitimate users share the same channel which is independent of the channels between the legitimate users and the eavesdropper, leading to secure transmissions. However, practical implementation of the physical layer security faces many challenges. First, for the correlated channel such as the multiple-input and multiple-output (MIMO) channel, the security is decreased due to the correlation between the generated secret bits. Second, the nearby eavesdropper posts a security threat due to observing the same channel as the legitimate user's. Third, the eavesdroppers might try to reconstruct the wireless environments. In this paper, we propose two practical physical layer security schemes for the MIMO orthogonal frequency-division multiplexing (MIMO-OFDM) systems: the precoding matrix index (PMI)-based secret key generation with rotation matrix (MOPRO) and the channel quantization-based (MOCHA) scheme. The former utilizes PMI and rotated reference signals to prevent the eavesdroppers from learning the secret key information and the latter applies channel quantization in order to extract more secret key bits. It is shown that not only the secure communication but also the MIMO gain can be guaranteed by using the proposed schemes.
A frequency domain (FD) time-reversal (TR) precoder is proposed to perform physical layer security (PLS) in single-input single-output (SISO) systems using orthogonal frequency-division multiplexing (OFDM) and artificial noise (AN) signal injection. The AN signal does not corrupt the data transmission to the legitimate receiver but degrades the decoding performance of the eavesdropper. This scheme guarantees the secrecy of a communication towards a legitimate user when the transmitter knows the instantaneous channel state information (CSI) of the legitimate link thanks to the channel reciprocity in time division duplex (TDD) systems, but does not know the instantaneous CSI of a potential eavesdropper. Three optimal decoding structures at the eavesdropper are considered in a fast fading (FF) environment depending on the handshake procedure between Alice and Bob. Closed-form approximations of the AN energy to inject in order to maximize the SR of the communication are derived. In addition, the required conditions at the legitimate receiver's end to guarantee a given SR are determined when Eve's signal-to-noise ratio (SNR) is infinite. Furthermore, a waterfilling power allocation strategy is presented to further enhance the secrecy of the scheme. Simulation results are presented to demonstrate the security performance of the proposed secure system.