## 6 Discussion  
It is evident that the e-Health Cloud presents promising opportunities for the healthcare industry which is still facing serious challenges. These challenges include patient care quality and safety, dramatically increasing healthcare costs, hardware costs and limitations, computing and access speeds, \begin{table}
\begin{tabular}{p{42.7 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt}} \hline \hline
**Work** & **Objective** & **Approach** & **Advantages** & **Limitations** \\ \hline
[64] & Secure personal health record (PHR). & Patient-Centric and fine-grained data access control through multiple-owner settings model. & Fine-grained access; user revocation; flexible data access policy; beak-glass access. & Computation overhead on data owner; risks of privacy exposure by cloud owner. \\ \hline
[65] & Secure PHR, maintain data confidentiality against cloud owner; reduce overhead on the data owner for key distribution and data/user management. & Allow data owner to delegate computation tasks in fine-grained data access control to cloud owners without disclosing content by combined advanced cryptographic techniques: key distribution and data/user (KP-ABE), Proxy Re-encryption (PRE) and lazy re-encryption. & Cloud owner is not able to learn any “plaintext medical data”; computation overhead is reduced on users which saves their efforts and time online; scalability. & Limited data access policies management; policy means management; emergency scenarios. \\ \hline
[66] & Ensure privacy and confidentiality of EHR; Track activities at the Cloud owner end of the e-Health Cloud infrastructure. & Install Computer forensic tools on the cloud machines to capture any volatile information. Different mechanisms of authentication, authorization and access control procedures to protect nonvolatile cloud infrastructure. & Protect medical data confidentiality against cloud owners; CFT provides digital evidence to be used to establish cyber crime in courts of law. & CFT promises to track confidentiality against cloud owners; covert devices in courts; but it does not physically stop volatile actions. & CFT promises to track volatile actions and to support cases in courts; support cases in courts; but it does not physically stop volatile actions. \\ \hline
[21] & Secure end user platforms when accessing e-Health Cloud. & Trusted privacy domains (TVD): Systems in the end-user platform should be able to divide the execution environment for applications into separated domains isolated from each other. & Overcome limitations of security features within end user platforms; reduce security risks; Automatic management (transparent TVD) establishment, key management and policers enforcement. & Hardware requirements; complexity and scalability \\ \hline
[17] & Secure EHR exchange when a referral is made. & EHR is only stored at the physicians’ practices (the only trusted environment). EHRs are encrypted and signed before leaving the physician’s practice and decrypted only by the receiving specialist. & Provides secure encryption and signatures for all documents transferred. & Patient and patient-centric functions are not integrated in the current model. \\ \hline
[58] & Develop and disseminate specialized secure services/platforms for e-Health Cloud. & Digital signature, hashing and encryption, integrity check-sum, Single Services/platforms for audit trial, identity mapping, _etc._ & A complete e-Health Cloud services platform, provides mechanisms to reinforce medical environment; medication with other security, integrity \& auditing. & Comprehensive evaluation in a real medical environment; medication with other public e-Health Clouds. \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Summary of various proposed security approaches. backup capabilities, security, resources scarcity; and most importantly, collaboration and knowledge sharing among healthcare professionals at local and international levels.