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The continuous growth of the users pool of Social Networking web sites such as Facebook and MySpace, and their incessant augmentation of services and capabilities will in the future, meet and compare in contrast with today's Content distribution Networks (CDN) and Peer-to-Peer File sharing applications such as Kazaa and BitTorrent, but how can these two main streams applications, that already encounter their own security problems cope with the combined issues, trust for Social Networks, content and index poisoning in CDN? We will address the problems of Social Trust and File Sharing with an overlay level of trust model based on social activity and transactions, this can be an answer to enable users to increase the reliability of their online social life and also enhance the content distribution and create a better file sharing example. The aim of this research is to lower the risk of malicious activity on a given Social Network by applying a correlated trust model, to guarantee the validity of someone's identity, privacy and trustfulness in sharing content.

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Now days, the online social networks (OSN) have gained considerable popularity. More and more people use OSN to share their interests and make friends, also the OSN helps users overcome the geographical barriers. With the development of OSN, there is an important problem users have to face that is trust evaluation. Before user makes friends with a stranger, the user need to consider the following issues: Can a stranger be trusted? How much the stranger can be trusted? How to measure the trust of a stranger? In this paper, we take two factors, Degree and Contact Interval into consideration, which produce a new trust evaluation model (T-OSN). T-OSN is aimed to solve how to evaluate the trust value of an OSN user, also which is more efficient, more reliable and easy to implement. Base on our research, this model can be used in wide range, such as online social network (OSN) trust evaluation, mobile network message forwarding, ad hoc wireless networking, routing message on Internet and peer-topeer file sharing network. The T-OSN model has following obvious advantages compare to other trust evaluate methods. First of all, it is not base on features of traditional social network, such as, distance and shortest path. We choose the special features of OSN to build up the model, that is including numbers of friends(Degree) and contact frequency(Contact Interval). These species features makes our model more suitable to evaluate OSN users trust value. Second, the formulations of our model are quite simple but effective. That means, to calculate the result by using our formulations will not cost too much resources. Last but not least, our model is easy to implement for an OSN website, because of the features that we used in our model, such as numbers of friends and contact frequency are easy to obtain. To sum up, our model is using a few resources to obtain a valuable trust value that can help OSN users to solve an important security problem, we believe that will be big step for development of OSN.

Mobile health (mHealth) applications have become ubiquitous and have enabled selfmonitoring to help provide better health outcomes. However, the wide availability of mHealth apps introduces new challenges when users need to download and use several apps. While past app evaluations have highlighted many issues, the surrounding work is limited. This study aims to analyse the current user challenges and expectations from future mHealth apps. This information is important to inform and guide the design of better and more attractive mHealth platforms of the future. For our empirical investigation of user feedback, we designed an anonymous online survey using key dimensions from the Mobile Application Rating Scale (MARS), the Technology Acceptance Model (TAM) and the Value Proposition Canvas. Our survey was distributed via online channels such as Twitter and LinkedIn, and we received 70 valid responses that indicated challenges such as functional overlaps between different apps, unnecessary features, and poor customizability. Similarly, most respondents expressed their preference for a single platform to manage their health. These challenges suggest the need to design more capable unified mHealth platforms that can be tailored to a user's needs. While the development of such platforms raise valid questions around the increase in software complexity and privacy concerns around user data, an open design can address these concerns and offer a better experience. Overall, these findings indicate the need for more research into mHealth app design strategies where the regular use of more than one app must be considered to create better, more engaging mHealth apps.INDEX TERMS mHealth, eHealth, mHealth apps, usability survey, user challenges, user expectations.