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Security poses a major challenge in ad hoc networks today due to the lack of fixed or organizational infrastructure. This paper proposes a modification to the existing “fully distributed certificate authority” scheme for ad hoc networks. In the proposed modification, redundancy is introduced by allocating more than one share to each node in order to increase the probability of creating the certificate for a node in a highly mobile network. A probabilistic analysis is carried out to analyze the trade-offs between the ease of certificate creation and the security provided by the proposed scheme. The analysis carried out from the intruder's perspective suggests that in the worst-case scenario, the intruder is just “one node” away from a legitimate node in compromising the certificate. The analysis also outlines the parameter selection criteria for a legitimate node to maintain a margin of advantage over an intruder in creating the certificate.

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Abstract-In this letter, we addressed the problem of estimating the time delay and the frequencies of noisy sinusoidal signals received at two spatially separated sensors. We employ the Propagator Method (PM) in conjunction with the well-known MUSIC/ root-MUSIC algorithm; the proposed method would generate estimates of the unknown parameters. Such estimates are based on the observation and/or covariance matrices. Moreover, the PM does not require the eigenvalue decomposition (EVD) or singular value decomposition (SVD) of the cross-spectral matrix (CSM) of received signals; therefore, a significant improvement in computational load is achieved. Computer simulations are also included to demonstrate the effectiveness of the proposed method.Index Terms-Delay and frequency estimation, MUSIC, propagator method, root-MUSIC.

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