Wireless secret key generation (WKG) methods based on wireless channel characterizations have gained significant interest as a mechanism for providing secure point-to-point communications. The secrecy of the generated wireless channel keys mainly depends on the spatial and temporal correlation properties of the channel which arises due to the channel's physical constraints. Ultra-wide band (UWB) WKG solutions can generate secure keys even when the two communicating parties and all objects within the environment in which they exist are stationary (i.e., in scenarios involving zero movement). But for a stationary environment successively generated secret keys are same which degrades the security of the system. Thus the proposed system to increase security is to generate secret keys using elliptic curve digital signature algorithm (ECDSA) and to transition the two communicating parties from using single antenna system to use multiple-input multiple-output (MIMO) antenna systems in combination with random beamforming as a solution to the undesirable effects of high temporal correlations in stationary environments. This allows adding directionality to the signal transmission and reception processes, which is unknown to the intruders. Security is further increased by increasing the number of antennas in the MIMO multiplexing system.
Wireless secret key generation (WKG) methods based on wireless channel characterizations have gained significant interest as a mechanism for providing secure point-to-point communications. The secrecy of the generated wireless channel keys mainly depends on the spatial and temporal correlation properties of the channel which arises due to the channel's physical constraints. Ultra-wide band (UWB) WKG solutions can generate secure keys even when the two communicating parties and all objects within the environment in which they exist are stationary (i.e., in scenarios involving zero movement). But for a stationary environment successively generated secret keys are same which degrades the security of the system. Thus the proposed system to increase security is to generate secret keys using elliptic curve digital signature algorithm (ECDSA) and to transition the two communicating parties from using single antenna system to use multiple-input multiple-output (MIMO) antenna systems in combination with random beamforming as a solution to the undesirable effects of high temporal correlations in stationary environments. This allows adding directionality to the signal transmission and reception processes, which is unknown to the intruders. Security is further increased by increasing the number of antennas in the MIMO multiplexing system.
Wireless secret key generation (WKG) methods based on communications channel characterizations have gained significant interest as a mechanism for providing secure point-to-point communications. Ultra-wide band (UWB) WKG solutions provide an advantage over narrow- and wide-band approaches in that they can generate secure keys even when Alice and Bob, the two communicating parties, and all objects within the environment in which they exist, are stationary (i.e., in scenarios involving zero movement). This creates a secondary problem in that the high temporal correlations of such environments can lead to successive WKG processes producing identical or nearly identical secret keys, whereas the ideal is that all generated keys from successive WKG processes should be independent. This work shows that one method available to address this problem is to move to multiple-input multiple-output (MIMO)-based antenna systems and the use of random beamforming. The security of the resulting approach is assessed with respect to the worst case scenario whereby the eavesdropper, Eve, is assumed to possess perfect knowledge of Alice and Bob's MIMO channel and is able to estimate, with some degree of error, the coefficients of Alice and Bob's independent random beamformers.
Wireless channel characterization is a known methodology for the generation of secret keys, where the secrecy of the key depends on the spatial-temporal correlation properties of the channel which themselves arise due to the channel's physical constraints. Spatial correlations can be suitably addressed simply by moving from narrow band channels to ultra-wide band (UWB) channels, but this does not address temporal correlations, (i.e., the likelihood that two successive key generation processes will generate the same, or nearly the same, key). This work shows that the worst-case of the temporal correlation problem, (i.e., when an eavesdropper has perfect knowledge of all past channel characterizations) is effectively addressed by applying channel prediction to the available ensemble of channel characterisation events and removing the predictable ensembles. It is shown that this proposed prediction approach increases the security of the key generation process while simultaneously reduce the available amount of information for the key generation. Moreover, real-world experimental data is also applied to confirm that a linear prediction suffices in this case.
Extracting secret key from the common randomness of wireless channel has gained significant interest as a mechanism for providing secure point-to-point communications. Current works focus on the methods of exploiting channel characterizations based on Received Signal Strength Indication (RSSI), channel phase and Channel Impulse Response (CIR) under different propagation environments. However, when the channel fading is static or quasi-static, the secret key bits derived from the channel may be identical or nearly identical. In this paper, we propose a method to solve this problem in multiple-input multiple-output (MIMO) systems based on random beamforming. Compared with single antenna systems, MIMO systems offer more randomness available. Furthermore we consider the worst scenario where the eavesdropper Eve knows perfect knowledge of the legitimate channel. The quantization error probability at Eve is simulated to assess the security of the proposed method.
This dissertation applies theories and concepts of wireless communications and signal processing to the security domain to assess the security of a Wireless secret Key Generation (WKG) system against capable eavesdroppers, who employ all the feasible tools to compromise the system’s security. The security of WKG is evaluated via real wireless measurements, where adversary knows and applies appropriate signal processing tools in ordere to predict the generated key with the communicating pair. It is shown that in a broadband stationary wireless communication channel, (e.g. commercial off-the-shelf 802.11 WLAN devices), a capable eavesdropper can recover a large portion of the secret key bits. However, in an Ultra-wideband (UWB) communication, at the same stationary environment, secret key rates of 128 bits per channel probe are achievable.
Encryption of confidential data with a secret key has become a widespread technique for securing wireless transmissions. However, existing key distribution methods that either deliver the secret key with a key distribution center or exchange the secret key using public-key cryptosystems are unable to establish perfect secret keys necessary for symmetric encryption techniques. This research considers secret key establishment, under the broad research area of information theoretic security, using the reciprocal wireless channel as common randomness for the extraction of perfect secret keys in multiple-input multiple-output (MIMO)communication systems. The presentation discusses the fundamental characteristics of the time-variant MIMO wireless channel and establishes a realistic channel simulation model useful for assessing key establishment algorithms. Computational examples show the accuracy and applicability of the model. The discussion then turns to an investigation of the influence of the spatial and temporal correlation of the channel coefficients on the bound of the key size generated from the common channel, and it is found that a sampling approach exists that can generate a key using the minimum sampling time. A practical key generation protocol is then developed based on an enhancement of a published channel coefficient quantization method that incorporates flexible quantization levels, public transmission of the correlation eigenvector matrix and low-density parity-check (LDPC) coding to improve key agreement. This investigation leads to the development of improved channel quantization techniques that dynamically shift the quantization boundaries at one node based on the information provided by the other node. Analysis based on a closed-form bound for the key error rate (KER) and simulations based on the channel model and measurement data show that the enhanced algorithms are able to dramatically reduce key mismatch and asymptotically approach the KER bound. Finally, other secret key generation algorithms based on channel-encryption rather than quantization are discussed, leading to a new concept for secret key generation using the common wireless channel.
Dynamic secret key generation from wireless channel characteristics is a promising technique for physical layer security. One of the important issues in this field is extending the secret key’s length while preserving its uniformity and randomness. This paper proposes a key generation method based on time-varying and the reciprocity of wireless channels for Multiple-Input Multiple-Output Orthogonal Frequency Division Multiplexing (MIMO-OFDM) wireless communication systems. In the proposed technique, the complex impulse response (CIR) of the estimated channel state information (CSI) is extracted, and a quantization algorithm is designed to convert the maximum peaks of the CIR into secret key bits. The effectiveness of the proposed key generation technique is assessed in terms of the randomness of the produced key bits with different key lengths by using a statistical test suite of the National Institute of Standards and Technology (NIST). The proposed technique is employed in the MIMO-OFDM systems with different modulation schemes through Additive White Gaussian Noise (AWGN) and Rayleigh channels. The simulation results show that the secret keys with various key lengths generated from the proposed technique for the MIMO-OFDM systems guarantee randomness. Moreover, the proposed CSI-based key generation technique provides better effectiveness in terms of security when compared to some existing techniques.