Cloud computing is an Internet‐based computing where the information technology resources are provided to end users following their request. With this technology, users and businesses can access programs, storage, and application development platforms through the Internet and via the services offered by the cloud service providers (CSPs). One of the biggest obstructions in the cloud computing environment is data security. Actually, the data are dispersed across multiple machines and storage devices such as servers, computers, and various mobile devices. The uncontrolled access to these resources and data leads to many important data security risks for the end users. In this way, and in order to ensure the reliability of the cloud and the trust of the users regarding this environment, controlling access to data and resources as well as protecting and ensuring their security becomes a critical task for CSPs. In this work, we present a comprehensive review of existing access control mechanisms used in the cloud computing environment. The advantages and disadvantages of each of these models are discussed and presented along with their analysis. Also, we study the cloud requirements of these models, and we evaluate existing control mechanisms against these requirements.

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Blockchain has been receiving considerable attention from the research community lately. Several research efforts have proposed the use of blockchain in many application domains. Not all of these application areas have received the same level of blockchain attention however and, for some of the applications, blockchain investigation has even stopped. Blockchain has the ability to shape the future, but not in all applications and topics. We explored those application areas that have not received much blockchain attention so that we can focus more on the application domains that have strong potential to reach the customer and have a high impact on the market. Based on our quantitative evaluation of blockchain applications and topics, we recommend those that need further investigation and implementation.

Abstract-The rapid development of medical sensors has increased the interest in Wireless Body Area Network (WBAN) applications where physiological data from the human body and its environment is gathered, monitored, and analyzed to take the proper measures. In WBANs, it is essential to design MAC protocols that ensure adequate Quality of Service (QoS) such as low delay and high scalability. This paper investigates Medium Access Control (MAC) protocols used in WBAN, and compares their performance in a high traffic environment. Such scenario can be induced in case of emergency for example, where physiological data collected from all sensors on human body should be sent simultaneously to take appropriate action. This study can also be extended to cover collaborative WBAN systems where information from different bodies is sent simultaneously leading to high traffic. OPNET simulations are performed to compare the delay and scalability performance of the different MAC protocols under the same experimental conditions and to draw conclusions about the best protocol to be used in a high traffic environment.