Guest Editors´ Introduction: Special Section on Cloud Computing Assessment: Metrics, Algorithms, Policies, Models, and Evaluation Techniques

This special issue deals with open problems related to Cloud computing assessment, and the interest raised in the scientific community is confirmed by the high quality of the papers received, which were selected after a review process started on July 2012 and ended on February 2013. Some relevant numbers are: 43 total submissions, nine papers accepted (approximately 0.2 acceptance ratio) after three rounds of reviews by more than 190 reviewers involved in the process. We would like to thank the authors of all the submitted papers for the high quality of their scientific contributions, and the prompt and timely reaction to the continual requests from the editors. We also thank all reviewers for their dedication and timeless efforts, which allowed us to select very high quality papers and respect the strict deadlines we have imposed. Different nonfunctional properties are considered in the special issue, mainly investigating Clouds behavior from the different perspectives of security and performance. For this reason we decided to split the special issue into two parts: the first that deals with security-related aspects (part I), and the second related to performance aspects (part II) of Cloud systems. Part I of this special issue addresses security aspects of Cloud computing such as trustworthiness, privacy, security vulnerabilities, countermeasures and threats to both physical (hardware) and logical (software, applications, data) architecture and infrastructure.