Secure Data Sharing in the Cloud
Danan Thilakanathan, Shiping Chen, Surya Nepal and Rafael A. Calvo

1 Introduction
Cloud systems [1, 2] can be used to enable data sharing capabilities and this can provide an abundant of benefits to the user. There is currently a push for IT organisations to increase their data sharing efforts. According to a survey by InformationWeek [3], nearly all organisations shared their data somehow with 74 % sharing their data with customers and 64 % sharing with suppliers. A fourth of the surveyed organisations consider data sharing a top priority. The benefits organisations can gain from data sharing is higher productivity. With multiple users from different organisations contributing to data in the Cloud, the time and cost will be much less compared to having to manually exchange data and hence creating a clutter of redundant and possibly out-of-date documents. With social networking services such as Facebook, the benefits of sharing data are numerous [4] such as the ability to share photos, videos, information and events, creates a sense of enhanced enjoyment in one’s life and can enrich the lives of some people as they are amazed at how many people are interested in their life and well-being. For students and group-related projects, there has been a major importance for group collaborative tools [5]. Google Docs provides data sharing capabilities as groups of students or teams working on a project can share documents and can collaborate with each other effectively. This allows higher productivity compared to previous methods of continually sending updated versions of a document to members of the group via email attachments. Also in modern healthcare environments, healthcare providers are willing to store and share electronic medical records via the Cloud and hence remove the geographical dependence between healthcare