The confidentiality of communications in the Internet of Things (IoT) is critical, with cryptography being currently the most widely employed method to achieve it. Establishing cryptographically secure communication links between two transceivers requires the pre-agreement on some key, unknown to an external attacker. In recent years there has been growing interest for techniques that generate a shared random key through observation of the channel and its effects on the exchanged messages. The maximum length of that key is characterised by the Mutual Information (MI) between the observations of the two radios. In this work we examine the practical limits of the MI of off-the-shelf transceivers communicating through the IEEE 802.15.4 specification in an indoor office environment, and calculate the secret-key capacity, that is, the maximum length of an extracted secret-key in the presence of an eavesdropper. Furthermore, we study how using groups of observations can affect the MI and both analytically and experimentally prove that grouping observations leads to better results and an increased key-capacity.
The confidentiality of communications in the Internet of Things (IoT) is critical, with cryptography being currently the most widely employed method to achieve it. Establishing cryptographically secure communication links between two transceivers requires the pre-agreement on some key, unknown to an external attacker. In recent years there has been growing interest for techniques that generate a shared random key through observation of the channel and its effects on the exchanged messages. The maximum length of that key is characterised by the Mutual Information (MI) between the observations of the two radios. In this work we examine the practical limits of the MI of off-the-shelf transceivers communicating through the IEEE 802.15.4 specification in an indoor office environment, and calculate the secret-key capacity, that is, the maximum length of an extracted secret-key in the presence of an eavesdropper. Furthermore, we study how using groups of observations can affect the MI and both analytically and experimentally prove that grouping observations leads to better results and an increased key-capacity.
Physical layer security (PLS) is a new paradigm aiming at securing communications between legitimate parties at the physical layer. Conventionally, achieving confidentiality in communication networks relies on cryptographic techniques such as public-key cryptography, secret-key distribution and symmetric encryption. Such techniques are deemed secure based on the assumption of limited computational abilities of a wiretapper. Given the relentless progress in computational capacities and the dynamic topology and proliferation of modern wireless networks, the relevance of the previous techniques in securing communications is more and more questionable and less and less reliable. In contrast to this paradigm, PLS does not assume a specific computational power at any eavesdropper, its premise to guarantee provable security via employing channel coding techniques at the physical layer exploiting the inherent randomness in most communication systems. In this dissertation, we investigate a particular aspect of PLS, which is secret-key agreement, also known as secret-sharing. In this setup, two legitimate parties try to distill a secret-key via the observation of correlated signals through a noisy wireless channel, in the presence of an eavesdropper who must be kept ignorant of the secret-key. Additionally, a noiseless public channel is made available to the legitimate parties to exchange public messages that are also accessible to the eavesdropper. Recall that key agreement is an important aspect toward realizing secure communications in the sense that the key can be used in a one-time pad scheme to send the confidential message. In the first part, our focus is on secret-sharing over Rayleigh fading quasi-static channels. We study the fundamental relationship relating the probability of error and a given target secret-key rate in the high power regime. This is characterized through the diversity multiplexing tradeoff (DMT) concept, that we define for our model and then characterize it. We show that the impact of the secrecy constraint is to reduce the effective number of transmit antennas by the number of antennas at the eavesdropper. Toward this characterization, we provide several schemes achieving the DMT and we highlight disparities between coding for the wiretap channel and coding for secret-key agreement. In the second part of the present work, we consider a fast-fading setting in which the wireless channels change during each channel use. We consider a correlated environment where transmit, legitimate receiver and eavesdropper antennas are correlated. We characterize the optimal strategy achieving the highest secret-key rate. We also identify the impact of correlation matrices and illustrate our analysis with various numerical results. Finally, we study the system from an energy-efficiency point of view and evaluate relevant metrics as the minimum energy required for sharing a secret-key bit and the wideband slope.
With the increasing demands for sharing confidential information among massive Internet of Things (IoT) devices in 5G and beyond wireless networks, many applications require the common secret key generation for a group of IoT devices. However, most of the existing works on physical layer secret key generation (PLKG) only focus on the pairwise key generation between two users, which is a low efficient and high cost to be extended to the scenarios of group key generation. In this work, we propose a new efficient multiple-input–multiple-output (MIMO) physical layer group secret key generation scheme to reduce the consumption of channel probing and improve the efficiency for group key generation. Different from current schemes, in the proposed scheme, the transmitter randomly generates the group secret key and directly broadcasts the downlink data symbols to the group users. At the receiver end, each group user can efficiently “observe” the common group key through the downlink broadcasting data symbols, while keeping perfect secrecy of the shared group key against eavesdroppers. The performance of reliability, security, and the group key generation rate is fully investigated, which shows the advantages of high efficiency, low consumption, and strong robustness of the proposed scheme. Extensive simulations are conducted to validate the effectiveness of the proposed scheme.
As aspects of our daily lives become more interconnected with the emergence of the Internet of Things (IoT), it is imperative that our devices are reliable and secure from threats. Vulnerabilities of Wi-Fi Protected Access (WPA/WPA2) have been exposed in the past, motivating the use of multiple security techniques, even with the release of WPA3. Physical layer security leverages existing components of communication systems to enable methods of protecting devices that are well-suited for IoT applications. In this work, we provide a low-complexity technique for generating secret keys at the Physical layer to enable improved IoT security. We leverage the existing carrier frequency offset (CFO) and channel estimation components of Orthogonal Frequency Division Multiplexing (OFDM) receivers for an efficient approach. The key generation algorithm we propose focuses on the unique CFO and channel experienced between a pair of desired nodes, and to the best of our understanding, the combination of the features has not been examined previously for the purpose of secret key generation. Our techniques are appropriate for IoT devices, as they do not require extensive processing capabilities and are based on second order statistics. We obtain experimental results using USRP N210 software defined radios and analyze the performance of our methods in post-processing. Our techniques improve the capability of desired nodes to establish matching secret keys, while hindering the threat of an eavesdropper, and are useful for protecting future IoT devices.
The increasing use of Internet of Things (IoT) also make data security a very importance. Traditional cryptographic methods are often unsuitable for IoT due to limited processing power and memory capacity, creating a need for lightweight yet effective security solutions. Physical Layer Key Generation (PLKG) offers a promising approach by utilizing the unique characteristics of wireless communication channels to generate secret keys without overloaded system demands. This paper show a performance analysis of Group Secret Key Generation in outdoor environments. The challenges are interfrence, physical obstacles, and dynamic changes in the communication channel was also the part of this analysis. The test results show that group secret key generation achieved optimal performance in Scenario 2, which given a correlation coefficient of 63 %, indicating strong channel similarity between nodes and a bit retention rate of 97.9 % after quantization and error correction. Scenarios 1, 3, and 4 also show a good performance, with correlation coefficients of41%,14%, and 35 %, and corresponding bit retention rates of93.1%,90.9%, and 95.2 %, on each tests. All scenarios successfully met the entropy thresholds required for cryptographic applications, which include that randomness and security of the generated keys was confirmed.
The confidentiality of communications in the Internet of Things (IoT) is critical, with cryptography currently being the most widely employed method of ensuring it. Establishing cryptographically secure communication links between two transceivers requires the pre-agreement on some key, unknown to an external attacker. In recent years there has been growing attention in techniques that generate a shared random key through observation of the channel and its effects on the exchanged messages. In this work we present SKYGlow, a novel scheme for secret-key generation, designed for IoT devices, such as IEEE 802.15.4 and Bluetooth Low Energy (BLE) transceivers. SKYGlow employs the Discreet Cosine Transform (DCT) of channel observations and Slepian-Wolf coding for information reconciliation. Real-life experiments have resulted in the creation of 128-bit secret keys with only 65 packet exchanges and with an entropy of 0.9978 bits, making our scheme much more energy-efficient compared with others in the existing literature.
The widespread presence of Internet of Things (IoT) and massive Machine Type Communications (mMTC) devices has made security management increasingly complex. Typically, security is established after authentication, which verifies the legitimacy of parties involved in data exchange. To achieve this, both symmetric and asymmetric cryptography are employed. However, asymmetric cryptography can be vulnerable to misconfigurations and cryptanalysis. It also requires more memory and processing power. In contrast, symmetric cryptography is better suited for IoT and mMTC due to its smaller memory footprint and lower susceptibility to cryptanalysis. However, it requires both parties to share a secret key and relies on complex key derivation algorithms. The distribution and management of these keys introduce additional risks, including the possibility of interception. As a result, there is extensive research into key derivation schemes that can minimize these risks and limitations. One promising approach leverages the physical communication channel, which inherently has high entropy and reciprocity, to derive private keys. In this contribution, we first propose a scheme to derive symmetric keys that minimizes information available to potential eavesdroppers, thereby enhancing system security. We then validate the scheme using both synthetic data and real-world IoT deployments-covering 2.4 GHz and 868 MHz frequencies in various indoor and outdoor mobility scenarios-achieving a 100% key agreement rate. Finally, we discuss the potential applications of this scheme in 6G umMTC (ultra mMTC) deployments.