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This paper deals with the H ∞ state estimation problem for a class of networked multi-rate time-varying systems with estimation error variance constraint. The redundant channel transmission scheme is employed to reduce the packet dropout rate and improve the quality of the data delivery. By utilizing the lifting technique, an augmented estimation error system is established with a uniform sampling rate. The objective of this paper is to design a time-varying state estimator such that, in the simultaneous presence of the asynchronous sampling, probabilistic packet dropouts as well as stochastic noises, the error dynamics of the state estimation satisfies both the prescribed H ∞ performance requirement and the prescribed estimation error variance constraints. Through intensive stochastic analysis, sufficient conditions are established to ensure the existence of the desired estimator whose parameters are determined by solving a set of recursive linear matrix inequalities. A numerical example is presented to show the validity of the proposed estimation strategy. [ABSTRACT FROM AUTHOR]

Abstract: We analyze the relationship between the notion of certificateless public key cryptography (CL-PKC) and identity-based schemes without a trusted private key generator (PKG), formally define the security of certificateless threshold signatures, and propose a concrete implementation based on bilinear pairings. To exhibit the security of our proposal, we develop the theory of simulatability and relationship between the certificateless threshold signatures and the underlying (non-threshold) ID-based signatures. We show that the proposed scheme is robust and existentially unforgeable against adaptively chosen message attacks under CDH assumption in the random oracle model. [Copyright &y& Elsevier]

In cloud computing scenarios, it is a common approach to encrypt the data before uploading in order to maintain the privacy. Public key encryption with equality test (PKEET) provides a generic solution to equality comparisons on encrypted data. Considering the practical requirements of PKEET in group user scenarios, Ling et al. presented a group public key encryption scheme with equality test (G-PKEET) by utilizing the computationally expensive bilinear pairing operations. In this paper, we propose an efficient and verifiable group public key encryption with equality test construction without bilinear pairings (GPKEET/BP). Our proposal is developed from a basic observation that two points determine a straight line, and is proven to be indistinguishable against the chosen-ciphertext attacks (IND-CCA) in the random oracle model under the computational Diffie-Hellman (CDH) assumption. Theoretical analysis shows that our construction only involves several modular exponentiations in the encryption, decryption and test algorithms. The theoretical results are well supported by experimental simulations, which show that the test algorithm of GPKEET/BP performs about 92 % faster than that of Ling et al.'s scheme. So our GPKEET/BP scheme turns out to be better suited for group ciphertext equality test situations. [ABSTRACT FROM AUTHOR]

A distributed set-membership filter is designed for a kind of systems with unknown but bounded (UBB) noises over wireless sensor networks. The Denial-of-Service (DoS) attacks and the fading effects on the sensor measurements are taken into account simultaneously. To reveal the fluctuations of network environment, the coefficients of the fading channels are described by uncertain variables which take values over an interval. The objective of this paper is to estimate the desired sets involving actual states of the plant by implementing the consistency tests among the state sets, the measured outputs and the neighbor information. A recursive scheme on zonotopes involving the real system state is established in light of the zonotopic method, where an outer approximation of the exact uncertain set is performed. Moreover, based on the proposed outer approximation minimization criterion, an optimization issue is proposed to seek the parameters of the intersection zonotope. Finally, two illustrative simulations are utilised to state the feasibility of the proposed filter. [ABSTRACT FROM AUTHOR]

In this paper, the finite-horizon H ∞ filtering problem is investigated for a class of linear discrete-time multi-rate systems with quantization effects under the stochastic communication protocol (SCP). The SCP is adopted to mitigate the undesirable data collision phenomenon resulting from the limited bandwidth of communication networks. Governed by a Markov chain, the SCP is employed to determine which sensor node should be granted the access right at each transmission instant. In order to cope with the difficulty caused by the asynchronous sampling, a lifting technique is utilized to convert the multi-rate system into a single-rate one with the identical slow sampling rate. The main purpose of the addressed problem is to design a set of time-varying filters for the multi-rate systems such that, for all admissible multi-sampling periods and quantization effects under the SCP, the H ∞ constraint is satisfied over a finite-horizon. By resorting to the complete square method and the Riccati difference equation (RDE) technique, sufficient conditions are established to ensure the existence of the desired filters. Then, the filter parameters are explicitly expressed in terms of the solution to two coupled backward RDEs. Finally, a numerical example is presented to demonstrate the effectiveness of the proposed filter design algorithm. [ABSTRACT FROM AUTHOR]

Abstract: In a proxy re-encryption scheme, a semi-trusted proxy is given special power that allows it to transform a ciphertext for Alice into a ciphertext for Bob without learning any information about the messages encrypted under either key. When a proxy re-encryption scheme is constructed in an identity-based setting, it means that a proxy converts a ciphertext encrypted under Alice’s identity into a ciphertext under Bob’s. Proxy re-encryption has become more and more popular these years due to the fact that it has many practical applications. In this paper, we present an IND-CCA2 secure identity-based proxy re-encryption scheme which has several useful properties, including, multi-use, unidirectionality, etc. Finding a unidirectional, multi-use, and CCA2-secure proxy re-encryption scheme is presented as an open problem by Green et al. Fortunately, our identity-based proxy re-encryption scheme is a solution to this problem. As a middleware for fulfilling our main goal, we also propose a new construction of identity-based encryption using random padding techniques. The security of our schemes is based on the standard decisional bilinear Diffie–Hellman assumption in the random oracle model. [ABSTRACT FROM AUTHOR]

Abstract: We present the concept of a certificate-based proxy decryption (CBPd) system with revocability, which has the following properties: (1) key-escrow freeness; (2) implicit certification; (3) revocability without public key change; and (4) fine-grained delegation. A concrete CBPd scheme is also proposed. The scheme is semantically secure against adaptive chosen plaintext attack (IND-CBPd-Rev-CPA) under the decisional bilinear Diffie-Hellman assumption in the standard model. We also give an enhanced scheme that is secure against adaptive chosen ciphertext attacks (IND-CBPd-Rev-CCA) in the standard model. [Copyright &y& Elsevier]