H. Ghasemzadeh; M. Tajik Khasss; H. Mehrara
Volume 9, Issue 2 , July 2017, , Pages 131-145
Abstract
Recently permutation multimedia ciphers were broken in a chosen-plaintext scenario. That attack models a very resourceful adversary which may not always be the case. To show insecurity of these ciphers, we present a cipher-text only attack on speech permutation ciphers. We show inherent redundancies ...
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Recently permutation multimedia ciphers were broken in a chosen-plaintext scenario. That attack models a very resourceful adversary which may not always be the case. To show insecurity of these ciphers, we present a cipher-text only attack on speech permutation ciphers. We show inherent redundancies of speech can pave the path for a successful cipher-text only attack. To that end, regularities of speech are extracted in time and frequency using short time Fourier transform. We show that spectrograms of cipher-texts are in fact scrambled puzzles. Then, different techniques including estimation, image processing, and graph theory are fused together in order to create and solve these puzzles. Conducted tests show that the proposed method achieves accuracy of 87.8% and intelligibility of 92.9%. These scores are 50.9% and 34.6%, respectively, higher than scores of previous method. Finally a novel method, based on moving spectrogram distance, is proposed that can give accurate estimation of segment length of the scrambler system.
H. Ghasemzadeh; A. Payandeh; M. R. Aref
Abstract
Due to wireless nature and hostile environment, providing of security is a critical and vital task in wireless sensor networks (WSNs). It is known that key management is an integral part of a secure network. Unfortunately, in most of the previous methods, security is compromised in favor of reducing ...
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Due to wireless nature and hostile environment, providing of security is a critical and vital task in wireless sensor networks (WSNs). It is known that key management is an integral part of a secure network. Unfortunately, in most of the previous methods, security is compromised in favor of reducing energy consumption. Consequently, they lack perfect resilience and are not fit for applications with high security demands. In this paper, a novel method is proposed to improve the security of key management system based on broadcast messages from the base station. Another problem with WSNs is the cryptographic materials (such as private keys) stored in dead nodes. Adversaries may exploit these nodes to mount more effective attacks. Any secure key management system should also address this problem. It is argued that in the proposed method keying materials of dead nodes lose their validity, and therefore are of no use for an adversary. Finally, it is shown through simulation that the proposed method is almost three times more energy-efficient than conventional certificate-based key management systems.