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Abstract: It would be interesting if a signcryption scheme in the standard model could be made certificateless. One of the interesting attempts is due to Liu et al. [Z. Liu, Y. Hu, X. Zhang, H. Ma, Certificateless signcryption scheme in the standard model, Information Sciences 180 (3) (2010) 452–464]. In this paper, we provide a cryptanalysis on this scheme by depicting two kinds of subtle public key replacement attacks against it. Our analysis reveals that it does not meet the basic requirements of confidentiality and non-repudiation. [Copyright &y& Elsevier]

Abstract: Álvarez et al., Information Sciences 179 (12) (2009) proposed a new key exchange scheme where the secret key is obtained by multiplying powers of block upper triangular matrices whose elements are defined over . In this note, we show that breaking this system with security parameters is equivalent to solving a set of linear equations with unknowns in , which renders this system insecure for all the suggested practical choices of the security parameters. [Copyright &y& Elsevier]

Abstract: Wang et al. [B. Wang, Q. Wu, Y. Hu, Information Sciences 177 (2007)] proposed a knapsack-based probabilistic encryption scheme with non-binary coefficients which enjoys a high density larger than 1.06 in the worst case. In this work, we successfully attack this scheme by showing that a public key and a restriction on system parameters allow the attacker to recover a secret key in a cubic time complexity using modular equations. This approach is much more efficient than the previous attack by Youssef [A.M. Youssef, Information Sciences 179 (2009)], in which lattice basis reductions are used. Recovering secret keys can be done within 4h and 4days when n =100 and 200, respectively. A simple modification that helps resist known attacks is also discussed. [Copyright &y& Elsevier]

Abstract: In this article, we introduce an application of swarm intelligence to distributed visual information retrieval distributed over networks. Based on the relevance feedback scheme, we use ant-like agents to crawl the network and to retrieve relevant images. Agents movements are influenced by markers stored on the hosts. These markers are reinforced to match the distribution of relevant images over the network. We tackle the use of the information gathered during previous search sessions. In order to match the different categories available on the network, we use several markers. Sessions searching for the same category will thus use the same makers. The system involves three learning problems: the selection of relevant markers regarding the searched category, the reinforcement of these markers and the learning of the relevance function. All of these problems are based on the relevance feedback loop. We test our system on a custom network hosting images taken from the well known TrecVid dataset. Our system shows a high improvement over classical content based image retrieval systems which do not use previous sessions information. [Copyright &y& Elsevier]

Abstract: This work concerns the tracking problem of uncertain Takagi–Sugeno (T–S) continuous fuzzy model with external disturbances. The objective is to get a model reference based output feedback tracking control law. The control scheme is based on a PDC structure, a fuzzy observer and a H ∞ performance to attenuate the external disturbances. The stability of the whole closed-loop model is investigated using the well-known quadratic Lyapunov function. The key point of the proposed approaches is to achieve conditions under a LMI (linear matrix inequalities) formulation in the case of an uncertain and disturbed T–S fuzzy model. This formulation facilitates obtaining solutions through interior point optimization methods for some nonlinear output tracking control problems. Finally, a simulation is provided on the well-known inverted pendulum testbed to show the efficiency of the proposed approach. [Copyright &y& Elsevier]

Abstract: Recently, Yang et al. proposed an efficient user identification scheme with key distribution, in which it is possible for the user to anonymously log into a system and establish a secret key shared with the system. Mangipudi and Katti later demonstrated a Deniable-of-Service (DoS) attack on the Yang et al. scheme and then proposed an improvement to withstand such an attack. However, this paper demonstrates an identity disclosure attack to show that neither schemes’ claimed user anonymity requirement can be achieved. We further propose a novel user identification scheme with key distribution preserving user anonymity for distributed computer networks. The proposed scheme not only withstands the attacks mentioned above, but also achieves the following: (i) user anonymity, (ii) key distribution, (iii) mutual authentication, and (iv) key confirmation. The performance of our scheme is of greater efficiency than that of previously proposed schemes in terms of communication costs and computational complexities. [Copyright &y& Elsevier]