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IEEE Military Communications Conference (MILCOM)

Environment Aware Secure Key Derivation via RF Sensing and ISAC in 5G/6G Systems

Robert Zakrzewski, Mark A Beach

Published Oct 6, 2025• 0 citations
Publisher

Abstract

As wireless networks evolve toward 5G and 6G, securing communications in dense, dynamic, and potentially adversarial environments becomes increasingly critical. Traditional cryptographic security, relying on symmetric or asymmetric key exchanges at higher layers or pre-provisioning, imposes significant operational complexity—especially in decentralized private networks and tactical deployments where infrastructure is limited and exposure to interception or cryptanalysis is high.This work introduces an environment-aware cryptographic key derivation method that utilizes 5G NR waveforms and Integrated Sensing and Communication (ISAC) principles, accompanied by updates to the security frameworks in 5G and next-generation 6G networks. It exploits radio channel reciprocity to extract highly correlated features observable only by legitimate transceivers, while inherently excluding spatially separated eavesdroppers.Our system derives shared secret keys directly from Channel State Information (CSI), achieving high-entropy keys with a 100% agreement rate and a high key generation rate between legitimate nodes. We demonstrate its robustness using software-defined radios operating in the 5G FR1 band, across diverse environments, while constraining the amount of publicly accessible information available to potential eavesdroppers.By embedding geographical awareness, this approach provides a physically secure key generation method, making it well-suited for 5G/6G systems, private networks, and ultra-massive Machine-Type Communication (umMTC) scenarios. The results highlight the potential of physical layer security for future wireless encryption frameworks with design considerations to maximize security and limit eavesdropping feasibility.

DOI
10.1109/milcom64451.2025.11310054

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As wireless networks evolve toward 5G and 6G, securing communications in dense, dynamic, and potentially adversarial environments becomes increasingly critical. Traditional cryptographic security, relying on symmetric or asymmetric key exchanges at higher layers or pre-provisioning, imposes significant operational complexity—especially in decentralized private networks and tactical deployments where infrastructure is limited and exposure to interception or cryptanalysis is high.This work introduces an environment-aware cryptographic key derivation method that utilizes 5G NR waveforms and Integrated Sensing and Communication (ISAC) principles, accompanied by updates to the security frameworks in 5G and next-generation 6G networks. It exploits radio channel reciprocity to extract highly correlated features observable only by legitimate transceivers, while inherently excluding spatially separated eavesdroppers.Our system derives shared secret keys directly from Channel State Information (CSI), achieving high-entropy keys with a 100% agreement rate and a high key generation rate between legitimate nodes. We demonstrate its robustness using software-defined radios operating in the 5G FR1 band, across diverse environments, while constraining the amount of publicly accessible information available to potential eavesdroppers.By embedding geographical awareness, this approach provides a physically secure key generation method, making it well-suited for 5G/6G systems, private networks, and ultra-massive Machine-Type Communication (umMTC) scenarios. The results highlight the potential of physical layer security for future wireless encryption frameworks with design considerations to maximize security and limit eavesdropping feasibility.
Widespread wireless communication demands robust security management to prevent adversaries from exploiting ubiquitous radio signals. Traditionally, such security is enforced through mitigation strategies implemented at higher layers using symmetric and/or asymmetric cryptography. However, this introduces increasing complexity, particularly due to the key derivation and exchange mechanisms required. This challenge is further exacerbated in private networks, which often necessitate configuration and deployment at the tactical or ad-hoc level in hostile environments, where physical interception or cryptanalysis by adversaries is a significant risk.To address this, we propose a solution that performs key derivation by exploiting 5G waveforms and integrated sensing and communication (ISAC). This approach enables the extraction of highly correlated data between legitimate parties by leveraging the reciprocity of radio channels, while preventing eavesdroppers from replicating the key derivation process.In this demonstration, we show that incorporating physical-layer information introduces geographical awareness between communicating parties, without compromising the entropy and keys generation rate. Furthermore, we demonstrate that our method effectively prevents eavesdroppers from obtaining the information needed to compromise the derived keys. Finally, we implement the system using software-defined radio within the 5G FR1 frequency bands, achieving a 100% key agreement rate with high entropy across a range of environments.
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.
The diverse application scenarios envisioned for sixth generation (6G) are characterized by the deep integration of sensing and ubiquitous connectivity, which imposes unprecedentedly stringent security requirements. However, due to the open nature of wireless channels, mobile communications systems always face severe information security threats such as falsification, spoofing, interception, and repudiation. Cryptography-based symmetric and asymmetric encryption techniques remain mainstream solutions for information protection. Symmetric encryption is efficient and secure for legitimate users but suffers from key-distribution difficulties over open wireless channels, whereas asymmetric encryption resolves this problem but faces increasing risks from quantum computing due to its reliance on structured mathematical hardness assumptions. In response to these limitations, physical layer security (PLS) has gained a great deal of research attention as a powerful security component that leverages the features of varying wireless channels. Existing PLS schemes can be broadly classified into two categories. The first one takes advantage of the legitimate link’s opportunistic channel-quality superiority over or different spatial-domain directions from the attacking link, which still faces many practical implementation difficulties. The second category is termed physical-layer key generation (PLKG). It extracts the unique features of the legitimate link’s channel variation, which is often reciprocal, as the source of secret key generation and therefore can naturally implement secure key distribution tasks. This advantage no doubt injects new vigor to symmetric encryption as a stronger protection approach. Following this trend, we in this paper concentrate on the PLKG techniques. Specifically, we present a comprehensive overview on existing PLKG schemes, discussing diverse secret key generation and reconciliation methods. We further investigate the model-driven and deep-learning-based approaches tailored for the scenario with imperfect channel reciprocity between the sender and receiver. After comprehensively reviewing major existing schemes, we further discuss a recently proposed PLKG design based on codeword reconstruction, which makes use of the strong error-correcting capability of the forward-error-correction (FEC) codes to effectively implement secure and consistent secret key generation between the legitimate sender and receiver. Finally, we share our opinions on the unsolved challenges and potential research directions dedicated to PLKG toward meeting the security requirements of 6G.
Next generation 5G wireless networks pose several important security challenges. One fundamental challenge is key management between the two communicating parties. The goal is to establish a common secret key through an unsecured wireless medium. In this paper, we introduce a new physical layer paradigm for secure key exchange between the legitimate communication parties in the presence of a passive eavesdropper. The proposed method ensures secrecy via pre-equalization and guarantees reliable communications by the use of Low Density Parity Check (LDPC) codes. One of the main findings of this paper is to demonstrate through simulations that the diversity order of the eavesdropper will be zero unless the main and eavesdropping channels are almost correlated, while the probability of key mismatch between the legitimate transmitter and receiver will be low. Simulation results demonstrate that the proposed approach achieves very low secret key mismatch between the legitimate users, while ensuring very high error probability at the eavesdropper.
The fifth generation (5G) and beyond wireless communications will transform many exciting applications and trigger massive data connections with private, confidential, and sensitive information. The security of wireless communications is conventionally established by cryptographic schemes and protocols in which the secret key distribution is one of the essential primitives. However, traditional cryptography-based key distribution protocols might be challenged in the 5G and beyond communications because of special features such as device-to-device and heterogeneous communications, and ultra-low latency requirements. Channel reciprocity-based key generation (CRKG) is an emerging physical layer-based technique to establish secret keys between devices. This article reviews CRKG when the 5G and beyond networks employ three candidate technologies: duplex modes, massive multiple-input multiple-output (MIMO) and mmWave communications. We identify the opportunities and challenges for CRKG and provide corresponding solutions. To further demonstrate the feasibility of CRKG in practical communication systems, we overview existing prototypes with different IoT protocols and examine their performance in real-world environments. This article shows the feasibility and promising performances of CRKG with the potential to be commercialized.
Physical layer security (PLS) can be used to pro-vide keyless and innately secure communications by exploiting the propagation characteristics of the wireless channel at the physical layer (PHY) layer to co-generate cipher keys for symmetric encryption. While existing methods use channel state information as input for secret key generation, we consider a novel approach that derives features from frequency-time domain representation of in-phase and quadrature (IQ) samples to derive initial keys with high agreement rate. A recurrent neural network (RNN) with a quadruplet loss function is trained based on spectrograms collected from bi-directional time-division duplex channel probing between the two parties and on spectrograms collected from a passive eavesdropper. Information reconciliation is achieved using Reed Solomon codes. At the last step of the protocol, a 512-bit cryptographic key is generated by feeding the reconciled bit sequence to the Secure Hash Algorithm 3. Our experiments with software-defined radios in both indoor and outdoor environments evaluate the proposed key generation system under different channel propagation environments and hardware inaccuracies. We demonstrate that the proposed RNN-assisted channel feature extractor trained on indoor channel probe data operates successfully in two outdoor setups and produces up to 70 amplified keys out of 100 probes exchanged between two trusted parties i.e., Alice and Bob, while the passive eavesdropper fails to directly predict any of the generated keys.