To secure the communications in cognitive radio networks (CRNs), a group secret key extraction scheme based on received signal strength (RSS) was proposed. This scheme employed relay nodes to extract a group secret key in the chain topology. Be more specific, nodes other than the head and the tail were considered as relay nodes, of which the RSS measurement of each adjacent pair was extracted. Then, each RSS measurement was quantified referring to predetermined thresholds to ensure the randomness of the generated key which was multiple RSS measurements related. Finally, the gray code was utilized to encode the quantified RSS measurements. In this paper, MATLAB was used to simulate the process of users establishing group secret key in Gaussian channel. By setting different levels of noise, the signal-to-noise ratio (SNR) varied from 0 dB to 30 dB. The results showed that the bit inconsistency rate increased with the number of nodes in the group and decreased with the increase of SNR. At the same time, the key generation rate of the proposed scheme under different conditions was analyzed by numerical analysis. It showed that the group secret key rate varied with the number of nodes in the group and SNR, which was opposite to the bit inconsistency rate. The proposed scheme outperforms contemporary ones with higher extraction efficiency and a lower communication cost as well.
To secure the communications in cognitive radio networks (CRNs), a group secret key extraction scheme based on received signal strength (RSS) was proposed. This scheme employed relay nodes to extract a group secret key in the chain topology. Be more specific, nodes other than the head and the tail were considered as relay nodes, of which the RSS measurement of each adjacent pair was extracted. Then, each RSS measurement was quantified referring to predetermined thresholds to ensure the randomness of the generated key which was multiple RSS measurements related. Finally, the gray code was utilized to encode the quantified RSS measurements. In this paper, MATLAB was used to simulate the process of users establishing group secret key in Gaussian channel. By setting different levels of noise, the signal-to-noise ratio (SNR) varied from 0 dB to 30 dB. The results showed that the bit inconsistency rate increased with the number of nodes in the group and decreased with the increase of SNR. At the same time, the key generation rate of the proposed scheme under different conditions was analyzed by numerical analysis. It showed that the group secret key rate varied with the number of nodes in the group and SNR, which was opposite to the bit inconsistency rate. The proposed scheme outperforms contemporary ones with higher extraction efficiency and a lower communication cost as well.
In this paper, we evaluate the effectiveness of secret key extraction from the Received signal strength (RSS) variations on the wireless channel between the two devices for private communication between them. We use real world measurements of RSS in a variety of environments and settings. The results from our experiments with 802.11-based laptops show that 1)An adversary can cause predictable key generation in these static environments, and 2)In dynamic scenarios where the two devices are mobile, high entropy bits are obtained . Building on the strengths of existing secret key extraction approaches, we develop an environment adaptive secret key generation scheme that uses an adaptive Cascade-based information reconciliation and privacy amplification. In our scheme, to provide good scalability in terms of the number of nodes, we utilize a combinatorial design of public-private key pairs, which means nodes combine more than one key pair to encrypt and decrypt messages. We also show that it provides controllable resilience when malicious nodes compromise a limited number of nodes before key revocation and renewal.
We evaluate the effectiveness of secret key extraction, for private communication between two wireless devices, from the received signal strength (RSS) variations on the wireless channel between the two devices. We use real world measurements of RSS in a variety of environments and settings. The results from our experiments with 802.11-based laptops show that in certain environments, due to lack of variations in the wireless channel, the extracted bits have very low entropy making these bits unsuitable for a secret key, an adversary can cause predictable key generation in these static environments, and in dynamic scenarios where the two devices are mobile, and/or where there is a significant movement in the environment, high entropy bits are obtained fairly quickly. Building on the strengths of existing secret key extraction approaches, we develop an environment adaptive secret key generation scheme that uses an adaptive lossy quantizer in conjunction with Cascade-based information reconciliation and privacy amplification. Our measurements show that our scheme, in comparison to the existing ones that we evaluate, performs the best in terms of generating high entropy bits at a high bit rate. The secret key bit streams generated by our scheme also pass the randomness tests of the NIST test suite that we conduct. We also build and evaluate the performance of secret key extraction using small, low-power, hand-held devices-Google Nexus One phones-that are equipped 802.11 wireless network cards. Last, we evaluate secret key extraction in a multiple input multiple output (MIMO)-like sensor network testbed that we create using multiple TelosB sensor nodes. We find that our MIMO-like sensor environment produces prohibitively high bit mismatch, which we address using an iterative distillation stage that we add to the key extraction process. Ultimately, we show that the secret key generation rate is increased when multiple sensors are involved in the key extraction process.
The broadcast nature of wireless communication imposes the risk of information leakage to adversarial or unauthorized receivers. Therefore, information security between intended users remains a challenging issue. Currently, wireless security relies on cryptographic techniques and protocols that lie at the upper layers of the wireless network. One main drawback of these existing techniques is the necessity of a complex key management scheme in the case of symmetric ciphers and high computational complexity in the case of asymmetric ciphers. On the other hand, physical layer security has attracted significant interest from the research community due to its potential to generate information-theoretic secure keys. In addition, since the vast majority of physical layer security techniques exploit the inherent randomness of the communication channel, key exchange is no longer mandatory. However, additive white Gaussian noise, interference, channel estimation errors and the fact that communicating transceivers employ different radio frequency (RF) chains are among the reasons that limit utilization of secret key generation (SKG) algorithms to high signal to noise ratio levels. The scope of this dissertation is to design novel secret key generation algorithms to overcome this main drawback. In particular, we design a channel based SKG algorithm that increases the dynamic range of the key generation system. In addition, we design an algorithm that exploits angle of arrival (AoA) as a common source of randomness to generate the secret key. Existing AoA estimation systems either have high hardware and computation complexities or low performance, which hinder their incorporation within the context of SKG. To overcome this challenge, we design a novel high performance yet simple and efficient AoA estimation system that fits the objective of collecting sequences of AoAs for SKG. Cognitive radio networks (CRNs) are designed to increase spectrum usage efficiency by allowing secondary users (SUs) to exploit spectrum slots that are unused by the spectrum owners, i.e., primary users (PUs). Hence, spectrum sensing (SS) is essential in any CRN. CRNs can work both in opportunistic (interweaved) as well as overlay and/or underlay (limited interference) fashions. CRNs typically operate at low SNR levels, particularly, to support overlay/underlay operations. Similar to other wireless networks, CRNs are susceptible to various physical layer security attacks including spectrum sensing data falsification and eavesdropping. In addition to the generalized SKG methods provided in this thesis and due to the peculiarity of CRNs, we further provide a specific method of SKG for CRNs. After studying, developing and implementing several SS techniques, we design an SKG algorithm that exploits SS data. Our algorithm does not interrupt the SS operation and does not require additional time to generate the secret key. Therefore, it is suitable for CRNs.
In recent years, the Internet of Things (IoT) becomes popular technology. The one aspect that makes important concern in IoT is the confidentiality of communications. For securing communication in IoT, cryptography algorithm such as symmetrical cryptography requires the secret key exchange process in a public wireless network to ensure the sameness of the secret key. However, the exchange of secret keys in the public wireless network can be exploited by adversaries. So, we present the secret key generation scheme that generates a shared random key through observation of the communication channel parameter i.e. Receive Signal Strength (RSS) between two devices that no need to exchange the secret key. We use Middle-Point quantization to convert the RSS into bit sequences and use Clover Filter to eliminate the error bits after the quantization process. Measurement results showed that the proposed scheme improves the performance of existing schemes if the interval used is 25. The proposed scheme improves the KGR 24 times and improves efficiency to 63%. While for KDR, the proposed scheme can decrease the KDR value of 67.9%. Also, in all scenarios, the proposed scheme can pass the NIST randomness test.
In symmetric cryptography systems have problems in the distribution of secret keys. The two users who will communicate require sharing keys through the public channel. The proposed solution to overcome these problems is to utilize information from the physical layer (e.g. RSS). Received Signal Strength (RSS) is an indicator for measuring the power received by wireless devices. The advantage of secret key extraction using physical layer information from a wireless channel is that it allows both devices within the transmission range to extract the secret key together. In this paper, we propose a secret key generation scheme adopted from an existing scheme with modifications to improve performance. Our proposed system is applied to static and dynamic conditions to test performance. The proposed algorithm is able to obtain a reduction in KDR (Key Disagreement Rate) up to 48.42% and an increase in the KGR (Key Generation Rate) up to 23.35% when compared to the existing scheme. Our proposed system also successfully passed the randomness using the NIST test with the approximate value of entropy generated 0.80 in static conditions and 0.81 in dynamic conditions.
Shared key generation between two users to exploit the randomness of wireless channels as a source of secret key bits extraction has become an attractive alternative to ensure security in a mobile environment. In this paper, we evaluate the performance of key extraction scheme using measurement results of Received Signal Strength (RSS) on several variations of settings and types of movement. We add the moving average method before the quantization process so our scheme becomes more adaptive to the low variation of RSS, and the use of modified Level Crossing Algorithm to reduce Key Disagreement Rate (KDR) due to half-duplex mode, device limitation, and different types of devices. The results show that our proposed schemes, compared with the existing scheme produce bit stream with the highest entropy, a significant decrease of KDR and passed randomness test from NIST statistical suite.