Medical data collected by wearable wireless sensor devices must be adequately secured. A prerequisite for mass deployment of these secure systems is the ability to periodically renew cryptographic keys without user involvement. Recent work has shown that two communicating devices can generate secret keys directly from measurements of their common wireless channel, which is symmetric but cannot be inferred in detail by an eavesdropper. These schemes may, however, yield mismatching keys at the two ends, requiring reconciliation mechanisms with high implementation and energy costs, unsuitable for resource-poor body-worn devices. In this work, we demonstrate a scheme for secret-key generation able to construct shared keys with near-perfect agreement, thereby avoiding reconciliation costs. Our specific contributions are: (1) we identify non-simultaneous probing of the channel by the link end-points as the dominant cause of channel measurement disagreement; (2) we develop a practical filtering scheme to reduce this disagreement, dramatically improving signal correlation between the two ends without affecting key entropy; and (3) we show that by restricting key generation to periods of significant channel fluctuation, we achieve near-perfect key agreement. We demonstrate in several representative body-worn settings that our scheme can generate secret bits with 99.8% agreement, and so yield near-perfect matching 128-bit keys approximately every half hour.
Medical data collected by wearable wireless sensor devices must be adequately secured. A prerequisite for mass deployment of these secure systems is the ability to periodically renew cryptographic keys without user involvement. Recent work has shown that two communicating devices can generate secret keys directly from measurements of their common wireless channel, which is symmetric but cannot be inferred in detail by an eavesdropper. These schemes may, however, yield mismatching keys at the two ends, requiring reconciliation mechanisms with high implementation and energy costs, unsuitable for resource-poor body-worn devices. In this work, we demonstrate a scheme for secret-key generation able to construct shared keys with near-perfect agreement, thereby avoiding reconciliation costs. Our specific contributions are: (1) we identify non-simultaneous probing of the channel by the link end-points as the dominant cause of channel measurement disagreement; (2) we develop a practical filtering scheme to reduce this disagreement, dramatically improving signal correlation between the two ends without affecting key entropy; and (3) we show that by restricting key generation to periods of significant channel fluctuation, we achieve near-perfect key agreement. We demonstrate in several representative body-worn settings that our scheme can generate secret bits with 99.8% agreement, and so yield near-perfect matching 128-bit keys approximately every half hour.
Reliable communication over Wireless Body Area Networks (WBANs) is an essential aspect of Wireless Body Area Networks (WBANs) because the physiological data flows between wearable sensor nodes is sensitive data. The convectional cryptography methods usually apply a lot of computational complexity as well as energy overhead besides which they are not going to fit in the ultra-low-power WBANs. In the current paper a light-weight, energy-efficient Physical Layer Key Generation (PLKG) scheme the possibilities of which based on the native randomness and reciprocity of the wireless channel is used to generate secure symmetric keys is presented. With WBANs, there is a lot of temporal and spatial dynamics in the human body and its surrounding environment, which causes great variability in channel characteristics, in terms of Received Signal Strength Indicator (RSSI) and Channel State Information (CSI). Such physical layer parameters can be used as perfect entropy sources in generation of unique, unpredictable secret keys with whose knowledge, communication between nodes is possible and mutually exclusive only. The channel probing in the proposed framework is also robust, multi-bit quantization is performed adaptively, information reconciliation is performed through error correction codes, and privacy amplification is made through cryptographic hashing. We have developed a resilient system against bit mismatch and efficiently against passively eavesdropping, we guarantee the secrecy of the generated keys under adversary situation. With realistic WBAN models simulation and experiment validation shows that the proposed approach is capable of generating keystokes with very high key generation rate (50 bps) and a bit mismatch rate of lower than 3 percent as compared to existing schemes that solely relied on RSSI, making this protocol more secure and reliable to use. In addition, the framework meets the statistical randomness requirements specified by NIST and it does not leak mutual information to eavesdroppers. The scheme allows real-time use on resource-constrained devices, e.g., wearable medical devices and health-monitoring sensor, as it has low computational and memory overhead. The findings establish the feasibility of employing physical layer properties to achieve secure WBANs communication without any pre-shared keys or a centralized trust paradigm, thus, opening the way to scalable and privacy-preserving healthcare systems.
This study proposes a lightweight, reciprocity-driven physical layer key generation scheme tailored for secure communication in Wireless Body Area Networks (WBANs). By harnessing the inherent randomness and temporal variation of on-body wireless channels, cryptographic keys are dynamically generated between wearable devices without reliance on pre-distributed secrets or computationally intensive algorithms. The protocol employs adaptive channel probing and quantization, followed by efficient error reconciliation and privacy amplification, ensuring strong key agreement even under mobility and diverse body movements. Experimental evaluations on a real WBAN testbed demonstrate high key generation rates, low bit mismatch, and resilience to passive eavesdropping, validating the scheme’s suitability for resource-constrained, low-power healthcare wearables. The results highlight the potential of physical-layer security as a practical solution for next-generation, privacy-aware health monitoring systems.
In this paper, experimental results are presented for an encrypted wireless link between two body-worn sensor nodes fully integrated onto textile antenna platforms. Wireless communication between two persons walking in an indoor environment occurs over a unique physical propagation channel. For the purpose of data encryption, channel measurements are performed at both sides of the link, providing highly correlated pseudo random number sequences, with envelope correlation coefficients always above 0.7. Signals captured by an eavesdropper are substantially decorrelated, with correlation coefficients always below 0.15, and are therefore not suitable for key extraction. The mutual information is also determined, providing extra insight into the key generating potential of the pseudo random sequences. Practical error free secret key generation on both sides of the link, with reconciliation by means of Hamming check bits, is performed successfully in all cases between legitimate parties. At the same time, an eavesdropper is unable to extract the secret key from measured signals, as confirmed by the key error rates, which are calculated for all possible signal combinations, resulting in a key error rate after reconciliation around 0.5 for most eavesdropper channels and remaining at least 0.3 in the worst-case scenario.
The physical layer secret key generation exploiting wireless channel reciprocity has demonstrated its viability and effectiveness in various wireless scenarios, such as the Internet of Things (IoT) network, mobile communication network, and industrial control system. Most of the existing studies rely on the quantization technique to convert channel measurements into secret bits for confidential communications. However, non-simultaneous packet exchanges in time-division duplex systems and noise effects usually induce inconsistent quantization results and mismatched secret bits. Although recent research has spent significant effort mitigating such non-reciprocity, it is still far from practical error-free key generation. Unlike previous quantization-based approaches, we take a different viewpoint to match the randomly manipulated (i.e., permuted or edited) channel measurements between a pair of users by minimizing their discrepancy holistically. Specifically, two novel secret key generation algorithms based on bipartite graph matching (BMSKG) and edited sequence alignment (SA-SKG) are developed. BM-SKG allows two users to generate the same secret key based on the permutation order of channel measurements, while SASKG aims to align the edited channel measurements between a pair of users for secret key agreement. In both algorithms, one user can preset the secret key and embed encrypted messages in the exchanged data packets, which reduces communication overheads in key generation. Extensive experimental results show that both BM-SKG and SA-SKG algorithms achieve error-free key agreement on channel measurements at a low cost under various scenarios.
Devices in the Internet of Things (IoT) are usually limited in computing resources and energy capacity, which means that encryption schemes with higher complexity are not suitable for them to ensure secure communication. As a promising solution to this problem, physical layer key generation suggests that shared secret keys can be generated from noisy wireless channel measurements to enhance the security of wireless communications. In this article, we propose a key generation scheme with extremely low implementation complexity, which allows physical layer key generation to be implemented on IoT nodes. First, we preprocess the channel measurements with simple moving average filtering before quantization to improve channel reciprocity. Next, a bidirectional difference quantization scheme is proposed to realize reliable quantization of channel measurements, which is ingenious in that the quantization process does not depend on quantization thresholds, and thus, the mismatched key bits caused by measurements close to quantization thresholds can be effectively avoided. Then, we propose an improved Cascade protocol to achieve lightweight and efficient information reconciliation. The simulation results show that our scheme can well balance the reliability and efficiency of key generation, and has excellent performance in terms of implementation complexity and key randomness.
Secure wireless communication requires the establishment of a secure channel, which is challenging and costly in a lot of scenarios. To provide secret keys for symmetric cryptosystems in wireless networks, previous research has studied the pairwise secret key generation based on the shared information between legitimate entities by exploiting the characteristics of the wireless channel. However, most of the variables they use are measured in the time domain, and heavily depend on the dynamic environments to get enough entropy. Fast key generation is impossible with stationary entities when the environment is relatively stable. To release this constraint, we choose the pairwise radio power spectrum as an alternative, i.e., the radio signal strength (RSS) measurements in the frequency domain, collected at two ends of a link to extract the keys. To our best knowledge, this variable is for the first time utilized in the secret key generation to get two highly correlated bit streams as ``fuzzy'' secret keys and advances the RSS measurements in the time domain in prior research. Instead of carrying out information reconciliation on the fuzzy keys, a traditional method to handle the inevitable mismatching between keys due to non-ideal working environments before using them, the design developed in this thesis uses the fuzzy keys directly in the proposed symmetric cryptosystem by borrowing the error correcting ability of Forward Error Correction code. The design can not only be used as a light-weight cryptosystem, but also distribute keys to support other cryptosystems. It's resistive to both passive and active attacks. In fact, the design is motivated by the spatial irregularity of the radio power spectrum, a critical observation that paves the function of the proposed mechanism and is carefully verified with both empirical experiments and theoretical analysis. Advisor: Ziguo Zhong