Numerous research efforts have been made recently on exploiting the randomness of wireless channels to generate secret keys. This channel state information (CSI) based key generation method relies on spatial independence between the legitimate and eavesdropping channels. In this paper, we propose a methodology to extract secret keys through side-channel information. Our methodology involves the capture of side-channel information leaked by the electronic instruments, either when measuring channel characteristics or during encryption/decryption for key confirmation. Secret keys are extracted via analysis of the side-channel information. We provide experiment results to demonstrate the feasibility of our proposed side-channel attack methodology.
Numerous research efforts have been made recently on exploiting the randomness of wireless channels to generate secret keys. This channel state information (CSI) based key generation method relies on spatial independence between the legitimate and eavesdropping channels. In this paper, we propose a methodology to extract secret keys through side-channel information. Our methodology involves the capture of side-channel information leaked by the electronic instruments, either when measuring channel characteristics or during encryption/decryption for key confirmation. Secret keys are extracted via analysis of the side-channel information. We provide experiment results to demonstrate the feasibility of our proposed side-channel attack methodology.
The recent research on randomness of wireless channels shows that the channel state information (CSI) can be harnessed to generate secret keys for wireless communications. This CSI-based key generation claims to be secure due to the spatial independence between the legitimate channel and the eavesdropping channel. However, this paper presents the discovery that the side-channel information about the security key may leak from the electronic instruments when they are measuring the CSI, when the instruments are encrypting/decrypting for key confirmation, or even when the device is communicating with the established key. Through analyzing the side-channel information, the secret keys can be extracted. The side-channel information could be obtained without approaching the legitimate transceiver, thus posing a serious threat to the CSI-based key generation.
The location-specific channel state information can be exploited to generate secret keys for wireless system services, In the multipath wireless environment. Its secrecy capacity was usually studied with the wiretap channel model. This paper proposes a side channel model which is even more threatening to the security of the physical layer randomness based secret keys. We present the information-theoretic analysis of the side channel model, and compare it with the wire-tap model. The analysis indicates that the secret key capacity of the side-channel will be lower than that of the wire-tap channel, especially with a fading scenario. We conduct MATLAB simulation of physical layer randomness based key generation and SPICE simulation of key extraction to observe the side channel leakage of the circuit. The simulation results confirm the consistency of the key bits, thus verifying the feasibility of our proposed side-channel attack scheme against the physical layer security.
Generating keys and keeping them secret is critical in secure communications. Due to the "open-air" nature, key distribution is more susceptible to attacks in wireless communications. An ingenious solution is to generate common secret keys by two communicating parties separately without the need of key exchange or distribution, and regenerate them on needs. Recently, it is promising to extract keys by measuring the random variation in wireless channels, e.g., RSS. In this paper, we propose an efficient Secret Key Extraction protocol without Chasing down Errors, SKECE. It establishes common cryptographic keys for two communicating parties in wireless networks via the realtime measurement of Channel State Information (CSI). It outperforms RSS-based approaches for key generation in terms of multiple subcarriers measurement, perfect symmetry in channel, rapid decorrelation with distance, and high sensitivity towards environments. In the SKECE design, we also propose effective mechanisms such as the adaptive key stream generation, leakage resilient consistence validation, and weighted key recombination, to fully exploit the excellent properties of CSI. We implement SKECE on off-the-shelf 802.11n devices and evaluate its performance via extensive experiments. The results demonstrate that SKECE achieves a more than 3x throughput gain in the key generation from one subcarrier in static scenarios, and due to its high efficiency, a 50% reduction on the communication overhead compared to the state-of-the-art RSS based approaches.
Physical layer encryption is a promising solution to provide transmission security for Internet-of-Things (IoT). To realize physical layer encryption, channel state information (CSI) as a random source to generate secret keys should be exploited. The reciprocity of wireless channel between legitimate communication nodes which is typically assumed for time division duplex (TDD) systems, is of critical importance to ensure the consistency in generated keys at two nodes. However, in practical TDD systems, due to the asynchronous measurement of CSI, the receiver noise and the the difference in hardware, etc., the reciprocity of channel measurements between legitimate parties is hard to be guaranteed, which makes physical layer key generation approach infeasible. To address this issue, we propose a wireless key generation scheme based on deep learning techniques. Firstly, a feature extraction network, which consists of two auto-encoders trained jointly, is developed to extract the common feature from the different yet correlated channel observations at two legitimate nodes, which will be used as the source to generate keys. Then a quantizer with an adaptive guard band width is devised to output a binary secret-key sequence from the feature vector. Numerical results show that the proposed scheme achieves remarkable improvement in terms of key disagreement rate (KDR) and key generation rate (KGR) compared existing counterparts in the literature.
We design and analyze a method to extract secret keys from the randomness inherent to wireless channels. We study a channel model for a multipath wireless channel and exploit the channel diversity in generating secret key bits. We compare the key extraction methods based both on entire channel state information (CSI) and on single channel parameter such as the received signal strength indicators (RSSI). Due to the reduction in the degree-of-freedom when going from CSI to RSSI, the rate of key extraction based on CSI is far higher than that based on RSSI. This suggests that exploiting channel diversity and making CSI information available to higher layers would greatly benefit the secret key generation. We propose a key generation system based on low-density parity-check (LDPC) codes and describe the design and performance of two systems: one based on binary LDPC codes and the other (useful at higher signal-to-noise ratios) based on four-ary LDPC codes.
Due to the broadcast nature of wireless channels, wireless communication is vulnerable to eavesdropping, message modification, and node impersonation. Securing the wireless communication requires the shared secret keys between the communicating entities. Traditional security schemes rely on public key infrastructures and cryptographic algorithms to manage secret keys. Recently, many physical-layer-based methods have been proposed as alternative solutions for key generation in wireless networks. These methods exploit the inherent randomness of the wireless fading channel to generate secret keys while providing information-theoretical security without intensive cryptographic computations. This article provides an overview of the existing PHY-based key generation schemes exploiting the randomness of the wireless channels. Specifically, we first introduce the fundamental and general framework of the PHY-based key generation schemes and then categorize them into two classes: received-signal-strength-based and channel- phase-based protocols. Finally, we present a performance comparison of them in terms of key disagreement probability, key generation rate, key bit randomness, scalability, and implementation issues.