## Security and Privacy Challenges in e-Health Cloud  
Security and privacy in the e-health and other domains are generally the same issues mostly raised as the Cloud clients look to move their data and applications to the Cloud [62]. Security and privacy protection of patients' records in the e-Health Cloud is of absolute importance and involves various requirements. First, the creation and maintenance of cloud-based healthcare e-records of any type should preserve content authenticity, integrity and privacy. Next, all healthcare data should be guarded in secure storage with protective access mechanisms and secure transmissions. Last but not least, the access and sharing of healthcare data should provide an end-to-end source verification, confidentiality and auditing capabilities. Thus, the common security and privacy issues in the e-Health Cloud include:  
* **Confidentiality:** ensuring that healthcare data is not accessed by unauthorized parties. * **Integrity:** ensuring the accuracy and consistency of healthcare data. * **Authentication:** ensuring that users are the persons they claim to be. * **Access control**: ensuring that users access only healthcare data that they are allowed to access based on their authentication and access levels. * **Non-repudiation:** ensuring that a party of a communication cannot deny having sent or received the data. * **Privacy:** ensuring that patients maintain the right to control what healthcare data is collected about them, how it is used, who uses it, who maintains it, and what purpose it is used for. * **Audit:** ensuring the safety of healthcare data and the e-Health Cloud overall system by recording and monitoring all users and data access activities. Research on the security issues surrounding e-Health Cloud has been growing fast over the last few years. The security in the context of the Cloud has a complex maze of issues that must be addressed. However according to [PERSON] _et al._[63] we should make a clear distinction between technical security risks facing any IT infrastructure and those risks imposed solely due to the nature of the Cloud. Risks arising from the specific characteristics of Cloud Computing, related to specific innovations in the cloud, prevalent to the intrinsic core cloud technology or state-of-the-art cloud offerings. As a result, when analyzing the security risks for the e-Health Cloud, it is similarly important to try to separate the different types of risks to simplify the process of incorporating adequate security measures. However, as we will see in the following examples, most approaches handle the problem as a holistic approach and try to resolve all issues at once. Here we present some security solutions and approaches that have been proposed to fulfill the requirements for securing the storage and providing access controls of healthcare data in the Cloud. One approach suggested that the best way to deal with the risks of privacy exposure is to allow patients who are PHR owners to have full control over the selective sharing of their PHR data [64]. So instead of the Cloud owner encrypting the patients' data, patients can generate their own decryption keys utilizing attribute-base encryption (ABE) and then distribute them to their authorized users. Patients will be able to choose in a fine-grained way which users can have access and to which parts of their PHR by encrypting the record according to a relevant set of attributes. Patients also maintain the right to revoke access privileges when they want to. This model creates a patient-centric PHR system within which multiple owners encrypt data according to their own ways using different sets of cryptographic keys.