A secret key generation scheme based on stochastic perturbation is proposed to improve the generated secret key rate for quasi-static channels in Internet of Things (IoT). First, the two legitimate nodes send training sequences to estimate the channel information and the initial key is obtained by quantization. Second, each sub-key in the initial key is classified, which the classification label is the column value in the stochastic perturbation matrix. Finally, each sub-key is combined with the corresponding stochastic perturbation sequence through XOR operation to obtain the perturbed key estimation sequence. The simulation results show that with the same SNR, the key generation rate based on stochastic perturbation is faster, and the correlation between the sub-keys is lower. The National Institute of Standards and Technology (NIST) randomness test shows that keys generated based on stochastic perturbation have better randomness.
A secret key generation scheme based on stochastic perturbation is proposed to improve the generated secret key rate for quasi-static channels in Internet of Things (IoT). First, the two legitimate nodes send training sequences to estimate the channel information and the initial key is obtained by quantization. Second, each sub-key in the initial key is classified, which the classification label is the column value in the stochastic perturbation matrix. Finally, each sub-key is combined with the corresponding stochastic perturbation sequence through XOR operation to obtain the perturbed key estimation sequence. The simulation results show that with the same SNR, the key generation rate based on stochastic perturbation is faster, and the correlation between the sub-keys is lower. The National Institute of Standards and Technology (NIST) randomness test shows that keys generated based on stochastic perturbation have better randomness.
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.
The wireless key generation using wireless channel reciprocity has attracted considerable attention in the past two decades. However, there are many challenges for the key generation in quasistatic wireless environments. The key generation rate (KGR) in a quasistatic environment is low, and the randomness of the key is insufficient, which is difficult to meet the secure communication requirements. To tackle these issues, a random permutation and perturbation-based wireless key generation (RPP-WKG) scheme is proposed to improve the KGR and randomness in quasistatic environments. Unlike existing key generation schemes, the RPP-WKG scheme allows the two legitimate users to generate the same secret key based on their random permuted channel measurements. Besides, the perturbed key sequence will be obtained by combining the initial key generated after quantization and the permutation order sequence through the XOR operation. Simulation results show that the proposed RPP-WKG scheme can generate secret keys with a high generation rate, sufficient randomness, a low mismatch rate, and a low correlation coefficient in quasistatic environments.
Physical layer secret key generation schemes can provide lightweight encryption for resource-constrained Internet of Things (IoT) devices. However, many IoT devices are stationary and the environment is usually static, which leads to ultra-low/zero secret key rates. To circumvent this problem, a novel secret key generation scheme based on Reconfigurable Intelligent Surface (RIS) is proposed for Multiple-Input Single-Output IoT communications. The RIS is introduced into the network, and the phase shifts at RIS are tuned randomly in each frame, which makes time-varying reflection channels superimposed on the original channels. And then, the secret key capacity of all nodes within the cell coverage area can be remarkably improved. Compared with the existing methods, the scheme is loosely coupled with the existing communication system. The closed-form expressions of secret key capacity taking into account eavesdropping are first derived for the case studies of independent and correlated channels. We can conclude that sharing the same phase shifts randomness will not bring key information leakage. Compared with existing user-introduced randomness schemes, the proposed scheme can maintain good performance as the number of eavesdropping nodes increases. Further, the impact of parameters, such as the number of reflecting units, the transmit antennas, and the Rician factor, on secret key performance are analyzed respectively, which can offer guidelines for system design. Finally, simulation results verify the theoretical analysis.
Physical layer secret key generation schemes can provide lightweight encryption for resource-constrained Internet of Things (IoT) devices. However, many IoT devices are stationary and the environment is usually static, which leads to ultra-low/zero secret key rates. To circumvent this problem, a novel secret key generation scheme based on Reconfigurable Intelligent Surface (RIS) is proposed for Multiple-Input Single-Output IoT communications. The RIS is introduced into the network, and the phase shifts at RIS are tuned randomly in each frame, which makes time-varying reflection channels superimposed on the original channels. And then, the secret key capacity of all nodes within the cell coverage area can be remarkably improved. Compared with the existing methods, the scheme is loosely coupled with the existing communication system. The closed-form expressions of secret key capacity taking into account eavesdropping are first derived for the case studies of independent and correlated channels. We can conclude that sharing the same phase shifts randomness will not bring key information leakage. Compared with existing user-introduced randomness schemes, the proposed scheme can maintain good performance as the number of eavesdropping nodes increases. Further, the impact of parameters, such as the number of reflecting units, the transmit antennas, and the Rician factor, on secret key performance are analyzed respectively, which can offer guidelines for system design. Finally, simulation results verify the theoretical analysis.
A novel secret key generation (SKG) method based on two-way randomness is proposed for TDD-SISO system. The legitimate transceivers mutually transmit their own random signal via reciprocal wireless channel, then the multiplication of transmitted and received signal is used as common randomness to generate secret keys. In quasi-static channel, the theoretical SKG rates (SKGRs) of the three SKG methods, namely wireless channel based, one-way randomness and two-way randomness, are derived and compared. Further, two practical SKG schemes based on two-way randomness, Scheme-1bit and Scheme-3bit, are completely designed and simulated. Generally, Scheme-1bit applies to low signal to noise ratio (SNR) scenarios and achieves 0.13~0.86bit/TsSKGR and 10-2~10-5level secret key outage probability (SKOP), while Scheme-3bit fits high SNR situation and obtains 0.93~1.35bit/TsSKGR and 10-3~10-4level SKOP. At last, the national institute of standards and technology (NIST) test is conducted to evaluate the secret key randomness (SKRD) and the test results show that both of the proposed schemes have passed the test.
Secret key agreement in distributed low-power networks, such as Internet of Things (IoT) networks, is a major requirement for deploying cryptographic protocols to protect the security of sensitive data. However, due to the distributed nature of such networks, the devices need to be able to generate secret keys locally from some common source of randomness. The randomness in the characteristics of the physical layer channel provides such sources, however, this can be quite limited if the devices operate in a static environment and experience static or very slow fading channel. Therefore, fast secret key generation in such environments while keeping a low complexity architecture for the network nodes, such as IoT devices, remains a challenging task. We design a low-complexity protocol for fast secret key generation in static environments. To this end, we propose to use a limited number of random bits independently generated by the legitimate parties, referred to as Alice and Bob, in combination with the fading parameter to create a common source of randomness. In the proposed protocol, Alice and Bob share their random bits over the public channel, assumed to be a fading channel, and then construct a common random sequence. Then they perform several steps for recovery from errors in the shared sequence, privacy amplification to limit the chances of a successful attack, and consistency checking by exploiting universal hash functions. We characterize the reliability of the proposed protocol and provide an upper bound on the probability of accepting a mismatched key by Alice and Bob. The eavesdropper Eve is assumed to be passive and a successful attack by her is the event of guessing the key right based on her observations. We provide an analytical upper bound, that can be numerically evaluated, on the probability of a successful attack by Eve using the cryptographic notion of semantic security. In the simulations, the proposed protocol achieves a bit generation rate of 64-96 bits/packet, bit mismatch rate of 11-24%, bit error rate of 0.005%, 50% randomness efficiency, the probability of successful attack of at most 2-31, and the probability of consistency checking failure of at most 2-16.