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Abstract-It has been shown that the radio channel impulse response for a pair of legitimate Ultra-wide band (UWB) transceivers can be used to generate secret keys for secure communications. Past proposed secret key generation algorithms under-exploited the available number of secret key bits from the radio channel. This paper proposes a new efficient method for generation of the shared key where the transceivers use LDPC decoders to resolve the differences in their channel impulse response measurements caused by measurement noise. To ensure secret key agreement, a method of public discussion between the two users is performed using the syndrome from Hamming (7,3) binary codes. An algorithm is proposed to check the equality of generated keys for both legitimate users, and ensure error-free secure communication. The security of this algorithm has been verified by AVISPA. Comparisons are performed with previous work on secret key generation and it has been shown that this algorithm reliably generates longer secret keys in standard UWB radio channels.

Secure communications in UWB based on cryptographic keys generated from channel measurements without a trusted third party have been developed. The fine time resolution of UWB allows high levels of mutual information to be obtained by a given A and B through independent characterizations of their shared communication channel. This mutual information determines the maximum secret key rate available to A and B. Since UWB channel gains change drastically with small antenna movements, it is inherently difficult for eavesdroppers to obtain channel measurementsand reduce the secret key rate. In essence, UWB can provide spatial-temporal specific secret keys. Upper bounds on the secret key rate for standard UWB channels are calculated. It is demonstrated that high secure key generation rates are possible. It is shown that these key rates can be generated over a wide range of signal to noise ratios and channel synchronization errors.

Abstract-Theoretical models of ultrawideband (UWB) radio channels indicate that pairs of UWB radio transceivers measure their common radio channel with a high degree of agreement and third parties are not be able to accurately estimate the state of the common channels. These properties allow generation of secret keys to support secure communications from UWB channels measurements. In this paper, the results of UWB propagation studies are presented that validate the required properties to support secret key generation in a typical indoor environment. Key generation algorithms are employed on the measured data and key lengths on the order of thousands of bits are obtained capable of supporting most popular cryptographic systems. The paper also reports measurements of the spatial and temporal correlation of the UWB channel from which the relative privacy of the secret keys can be determined as well as the rate new secret keys may be generated.

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