SUMMARY'Organization signature is a new variant of digital signature in organization transactions. It allows the employee in the organization to generate the message signature through his affiliation rather than his personal description. Certificateless public key cryptography solved the key escrow problem in identity-based cryptography, and the certificate distribution in the traditional public key infrastructure. In this paper, we present a provable secure pairing-free certificateless organizational signature scheme. Our scheme is more computationally efficient because it does not depend on pairings. The new scheme is provably secure in the random oracle model, assuming the hardness of elliptic curves discrete logarithm problem.'

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Summary Most recent research on channel‐based key generation oriented to time division duplex system because the channel reciprocity feature is applied directly for secret key generation. Most of commercial cellular systems depend on frequency division duplex (FDD) systems. In this paper, we investigate the impact of uplink and downlink of FDD systems for the generation of shared secret keys between two parties in the presents of passive eavesdropper. In addition, we are considering improving the rate of the secret key for wireless communication in FDD mode. The main idea is to use the fading coefficient of the channels between the relay and other parties as an additional random common source for the secret key generation. Also, explore the using of channel estimation techniques to reduce the channel training sequence and study its effect on the generation of shared key for wireless communications in FDD mode. We derive the upper bound of the generated shared key rate for four scenarios and give numerical examples to reveal the performance of our suggested improvement approaches.

Most of the current research on generating a secret key from wireless fading channels relies on the channel reciprocity feature of the time division duplex link between legitimate entities so that they can acquire related information from the joint wireless connection. This paper investigates the challenge of generating a shared secret key in frequency division duplex communication systems, in which there is no reciprocity between the two nodes, in the presence of an active opponent. We suggest a key generation algorithm that depends on the product of two fading coefficients. We additionally look at the effects of an interfering adversary on the suggested key establishment scheme and solve the problem of evaluating the key rate for a scheme depending on virtual channel gain. We illustrate an adversary model using an optimal attacking strategy to minimize the rate of generating a shared secret key for our suggested algorithm. Additionally, we identify the suitable channel conditions for the non‐zero rate in the existence of an interfering adversary using simulation results.