A Survey on Data Confidentiality and Privacy in Cloud Computing <s> CHALLENGES OF DATA SECURITY IN THE CLOUD <s> With the development of cloud computing, Data security becomes more and more important in cloud computing. This paper analyses the basic problem of cloud computing data security. With the analysis of HDFS architecture, we get the data security requirement of cloud computing and set up a mathematical data model for cloud computing. Finally we build a data security model for cloud computing. <s> BIB001 </s> A Survey on Data Confidentiality and Privacy in Cloud Computing <s> CHALLENGES OF DATA SECURITY IN THE CLOUD <s> Cloud Computing is becoming a well-known buzzword nowadays. Many companies, such as Amazon, Google, Microsoft and so on, accelerate their paces in developing Cloud Computing systems and enhancing their services to provide for a larger amount of users. However, security and privacy issues present a strong barrier for users to adapt into Cloud Computing systems. In this paper, we investigate several Cloud Computing system providers about their concerns on security and privacy issues. We find those concerns are not adequate and more should be added in terms of five aspects (i.e., availability, confidentiality, data integrity, control, audit) for security. Moreover, released acts on privacy are out of date to protect users' private information in the new environment (i.e., Cloud Computing system environment) since they are no longer applicable to the new relationship between users and providers, which contains three parties (i.e., Cloud service user, Cloud service provider/Cloud user, Cloud provider). Multi located data storage and services (i.e., applications) in the Cloud make privacy issues even worse. Hence, adapting released acts for new scenarios in the Cloud, it will result in more users to step into Cloud. We claim that the prosperity in Cloud Computing literature is to be coming after those security and privacy issues having be resolved. <s> BIB002 </s> A Survey on Data Confidentiality and Privacy in Cloud Computing <s> CHALLENGES OF DATA SECURITY IN THE CLOUD <s> The paper describes the modeling design of data security in Cloud Computing. Data security can be defined as confidence and integrity maintenance of data processed by an organization. In the paper, dealing with data security in all layers of cloud computing is discussed. The standard cloud storage uses three-level data security model in cloud computing which can be extended by a forth level responsible for the data integrity check. The model of data security in cloud computing was designed as an expansion of the present standard use of data storage model in cloud computing. The paper presents the design of a four-level data security model in cloud computing within which by the use of Petri nets it describes each part of data security in cloud computing. <s> BIB003
Security is a critical property of information systems and technologies. Currently, the security of Cloud systems pose a serious concern and risk for organisations who store data in the Cloud. According to Chia  , trio CIA is the elementary data security concept, which defines the three essential attributes of data security, i.e., confidentiality, integrity, and availability. Data stored in the Cloud can be accessed through various layers. To meet the three above-mentioned security attributes, it is necessary that all the accessible Cloud layers are defended in order to guarantee the security and privacy of data and data owners. According to Yuefa Dai et al. BIB001 , there are three major levels of defence. In the first level, users are verified, authenticated, and issued with digital signatures. The second level provides data protection using encryption. The third level is responsible for the users' data recovery by offering quick decryption services. The principle of availability is that all data and information is constantly accessible at the level required by the user. Hardening and redundancy are two approaches used to provide the availability of Cloud systems BIB002 . In terms of hardening, most of the Cloud computing system providers supply platforms and infrastructures placed on virtual machines. For example, Xen is a virtual machine used by Amazon, which is able to provide separate storage and memory virtualization. Virtualization offers the ability to meet service demand from a large number of users, while allowing service providers to secure their system by managing, blocking, and filtering traffic based on IP addresses and ports only. Moreover, large cloud computing system vendors are able to offer geographic redundancy in their Cloud infrastructure. Using different zones, Cloud providers can greatly reduce and protect the system from disruption or failure in a particular location, which can enhance the overall availability of the system (ibid). Data integrity refers to the data and information storage in the cloud being valid and protected from malicious or accidental modification or changes BIB003 . Data integrity can aid in detecting data manipulation. In the Cloud, data could be lost or damaged during transmission to or from Cloud data storage. Hence, Cloud service providers should check and maintain the data and computation continuously to prove that the data is intact and in order to detect any potential modification to the data (ibid). Confidentiality is another essential requirement to ensure the privacy and security of data in the Cloud through applying policies and rules that can limit the access to stored data. To obtain confidentiality in the Cloud, there are two approaches, namely, physical isolation and cryptography. According to Zhou et al. BIB002 , physical isolation cannot be achieved due to the fact that Cloud system offerings, such as data and services, are transferred through public networks. Virtual local area networks and networks' middle boxes, such as firewalls, can be an alternative way to obtain virtual physical isolation. For example, Amazon's vertica deploys the database EC2 and supplies VPNCubed and firewall to secure its database. Amazon's vertica database EC2 allows users to access and secure the system through a VPN between the client and vertica, and it provides a firewall to the outside world (ibid). Cryptography provides a more reliable option to ensure data confidentiality. Encryption is the predominantly used method of securing data in storage or during transmission