Device-to-device communication is increasingly important for emerging wireless applications, including the Internet of Things and industry mobile networks. To establish a secure communication channel between multiple legitimate devices, key agreement is an essential first step. Physical layer channel information is a promising technology for achieving communication security by generating a shared channel key. In this paper, we propose an efficient and random method for generating channel keys based on channel state information (CSI). Firstly, we preprocess the available subcarriers to reduce the correlation of adjacent subcarriers. Secondly, we propose a novel quantization process to generate random and secure channel keys. The part consists of two phases: the quantization phase and the inconsistency removal phase. In the quantization stage, CSI sub carriers are grouped into small blocks, and appropriate thresholds are generated. Then, wireless users quantize the CSI subcarriers into initial bit streams of 0 and 1 with different thresholds. In the inconsistency removal phase, we design an error correction mechanism where wireless users exchange the discarded index sequences in the initial bit streams to achieve key sequence consistency. We implement the proposed scheme using off-the-shelf wireless devices and evaluate its performance. The experimental results show that each CSI packet can produce 30 bits, which have passed the NIST randomness tests.
Device-to-device communication is increasingly important for emerging wireless applications, including the Internet of Things and industry mobile networks. To establish a secure communication channel between multiple legitimate devices, key agreement is an essential first step. Physical layer channel information is a promising technology for achieving communication security by generating a shared channel key. In this paper, we propose an efficient and random method for generating channel keys based on channel state information (CSI). Firstly, we preprocess the available subcarriers to reduce the correlation of adjacent subcarriers. Secondly, we propose a novel quantization process to generate random and secure channel keys. The part consists of two phases: the quantization phase and the inconsistency removal phase. In the quantization stage, CSI sub carriers are grouped into small blocks, and appropriate thresholds are generated. Then, wireless users quantize the CSI subcarriers into initial bit streams of 0 and 1 with different thresholds. In the inconsistency removal phase, we design an error correction mechanism where wireless users exchange the discarded index sequences in the initial bit streams to achieve key sequence consistency. We implement the proposed scheme using off-the-shelf wireless devices and evaluate its performance. The experimental results show that each CSI packet can produce 30 bits, which have passed the NIST randomness tests.
The traditional wireless communication security technology is based on cryptography at the network layer, which exploits computational complexity to make it difficult to crack to achieve encryption. With the ongoing advancement of computing power, computational security may be difficult to maintain. From the viewpoint of information theory, physical layer security technology is an essential instrument for integrating security and communication. This paper mainly studies the quantization steps in the key generation technology of wireless communication physical layer. In this paper, a quantization scheme with extremely low implementation complexity is proposed for key generation. Firstly, utilizing the reciprocity and randomness of the wireless channel, the communication parties conduct channel measurements to collect channel state information (CSI) and study the improvement of CSI extraction by incorporating intelligent reflection surfaces. Then, the proposed hybrid quantization scheme makes full use of CSI and quantizes the CSI and its phase information to obtain key bits. Numerical results show that the proposed scheme improves the quality of key generation and avoids information leakage during transmission, and passes the NIST randomness test.
Due to the reciprocity of wireless channels, the communication parties can directly extract the shared key from channel. This solution were verified through several schemes. However, in real situations, channel sampling of legitimate transceivers might be impacted by noises and other interferences, which makes the channel states obtained by initiator and responder might be obvious different. The efficiency and even availability of physical layer key generation are thus reduced. In this paper, we propose a lightweight and efficient physical layer key generation scheme, which extract shared secret keys from channel state information (CSI). To improve the key generation process, the discrete cosine transform (DCT) is employed to reduce differences of channel states of legitimate transceivers. Then, these outputs are quantified and encoded through multi-bit adaptive quantization(MAQ) quantizer and gray code to generate binary bit sequence, which can greatly reduce the bit error rate. Moreover, the low density parity check (LDPC) code and universal hashing functions are used to achieve information reconciliation and privacy amplifification. By adding preprocessing methods in the key generation process and using the rich information of CSI, the security of communications can be increased on the basis of improving the key generation rate. To evaluate this scheme, a number of experiments in various real environments are conducted. The experimental results show that the proposed scheme can effificiently generate shared secret keys for nodes and protect their communication.
Generating keys and keeping them secret is critical in secure communications. Due to the "open-air" nature, key distribution is more susceptible to attacks in wireless communications. An ingenious solution is to generate common secret keys by two communicating parties separately without the need of key exchange or distribution, and regenerate them on needs. Recently, it is promising to extract keys by measuring the random variation in wireless channels, e.g., RSS. In this paper, we propose an efficient Secret Key Extraction protocol without Chasing down Errors, SKECE. It establishes common cryptographic keys for two communicating parties in wireless networks via the realtime measurement of Channel State Information (CSI). It outperforms RSS-based approaches for key generation in terms of multiple subcarriers measurement, perfect symmetry in channel, rapid decorrelation with distance, and high sensitivity towards environments. In the SKECE design, we also propose effective mechanisms such as the adaptive key stream generation, leakage resilient consistence validation, and weighted key recombination, to fully exploit the excellent properties of CSI. We implement SKECE on off-the-shelf 802.11n devices and evaluate its performance via extensive experiments. The results demonstrate that SKECE achieves a more than 3x throughput gain in the key generation from one subcarrier in static scenarios, and due to its high efficiency, a 50% reduction on the communication overhead compared to the state-of-the-art RSS based approaches.
Physical layer key generation is an important handshaking step for establishing secure wireless communication in wireless networks. Existing methods based on fine-grained Channel State Information (CSI) have seen significant limitations. Reciprocity, the theoretical basis of physical layer key generation, is sensitive to factors such as noise, interference and hardware level variations. Feedback-based Channel Gain Complement is designed to conquer the imperfect reciprocity between two communication parties in actual environments. In addition, we have found that the adjacent subcarriers are strongly correlated. Quantizing all 30 subcarriers without discrimination will reduce the randomness and strength of the secret key while discarding some carriers will lose important information. We propose a cluster-based quantization method, which balances between the generation speed and consistency in initial key bits. Evaluation results in static and mobile scenarios have shown that under the sampling rate of 5 packet/sec, Bit Generation Rate can reach 20~ 26 bps, and the generated key sequence can pass the NIST standard randomness test.
Physical layer encryption is a promising solution to provide transmission security for Internet-of-Things (IoT). To realize physical layer encryption, channel state information (CSI) as a random source to generate secret keys should be exploited. The reciprocity of wireless channel between legitimate communication nodes which is typically assumed for time division duplex (TDD) systems, is of critical importance to ensure the consistency in generated keys at two nodes. However, in practical TDD systems, due to the asynchronous measurement of CSI, the receiver noise and the the difference in hardware, etc., the reciprocity of channel measurements between legitimate parties is hard to be guaranteed, which makes physical layer key generation approach infeasible. To address this issue, we propose a wireless key generation scheme based on deep learning techniques. Firstly, a feature extraction network, which consists of two auto-encoders trained jointly, is developed to extract the common feature from the different yet correlated channel observations at two legitimate nodes, which will be used as the source to generate keys. Then a quantizer with an adaptive guard band width is devised to output a binary secret-key sequence from the feature vector. Numerical results show that the proposed scheme achieves remarkable improvement in terms of key disagreement rate (KDR) and key generation rate (KGR) compared existing counterparts in the literature.
Internet-of-Things (IoT) networks generally contain resource-constrained devices that require an energy-efficient key generation procedure to producing secure keys at a faster rate. The physical characteristics of the wireless channel can be exploited to secure communication within IoT networks. In particular, secret keys can be generated by leveraging on the randomness of the wireless physical channel between two communicating parties. The conventional mechanism of generating keys at the physical layer, i.e., using channel probing, quantization, information reconciliation, and privacy amplification, may not be preferable for IoT devices. In addition, in some cases IoT devices may be deployed in static environments, wherein the channel coherence time is too high to generate keys at a faster rate and with the desired randomness. This study proposes a mapping table-based key distribution scheme for IoT environments, wherein multiple characteristics of the random channel are combined to improve not only the key generation rate (KGR) but also the key agreement rate (KAR) and bit error rate (BER). In the proposed scheme, both the channel magnitude and the phase are exploited in the key generation process. The proposed scheme is immune to channel estimation errors while providing sufficient randomness in the static environment. Additionally, the scheme is thoroughly investigated for different scenarios including the case of a smarter eavesdropper, which attempts to estimate the channel between the legitimate nodes. This case verifies the robustness of the proposed scheme in different settings and attack models.