Trust management becomes an urgent requirement in the cloud environment and a trust relationship between service user and service provider is required. Trust is the estimation of the ability of cloud resources in completing a task based on some criteria such as availability, reliability, and resource processing power. In this paper, an enhanced QoS-based model for evaluating the trustworthiness of the cloud provider is introduced. The proposed model calculates the accumulative trust value which is updated dynamically at each transaction and reflects the current or latest transaction of the provider in the cloud. The trustworthiness of a cloud resource is evaluated based on its provider reputation history from user feedback ratings based on the covariance mathematical technique to evaluate the credibility of the user's feedback. The trustworthiness of a cloud resource is also evaluated by calculating the computing power of resources at run-time. Experimental results confirm the effect of user opinion and resources processing speed on trust value calculation, which in turn assesses the trustworthiness of the cloud provider. The simulation has been performed using the CloudSim with the platform Eclipse for developing the proposed model.

Abstract. Cloud service composition is usually long term based and economically driven. Services in cloud computing can be categorized into two groups: Application services and Computing Services. Compositions in the application level are similar to the Web service compositions in Service-Oriented Computing. Compositions in the computing level are similar to the task matching and scheduling in grid computing. We consider cloud service composition from end users perspective. We propose Genetic Algorithm-based approach to model the cloud service composition problem. A comparison is given between the proposed composition approach and other existing algorithms such as Integer Linear Programming. The experiment results proved the efficiency of the proposed approach.

In this paper, a new design of hybrid plasmonic photonic crystal (PhC) waveguide is proposed and analyzed at operating wavelength of 1550 nm. The suggested design consists of hybrid cylindrical core with periodic grating as a cladding region. The effective index (neff), propagation length (Lp), and normalized mode effective area (Aeff) of the supported modes are numerically investigated using full vectorial finite element method. The cladding geometry is tuned to obtain long propagation length with good field confinement. The reported plasmonic PhC with uniform grating achieves long propagation length and low propagation loss of 124 µm, and 0.035 dB/µm respectively. Further, the PhC with chirped cladding offers propagation length and low propagation loss of 162 µm, and 0.0268 dB/µm at λ = 1550 nm, respectively.

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