A Survey on Data Confidentiality and Privacy in Cloud Computing <s> CRITICAL REVIEW OF SOLUTIOS TO DATA CONFIDENTIALITY IN THE CLOUD <s> Healthcare data has stringent security requirements for confidentiality, availability to authorized users, and traceability of access. The focus of this study is to investigate on these requirements and propose a solution for healthcare cloud providers that will help in protecting patient' data they host, which is of high importance. The focus will be on specific cloud computing healthcare security concerns and how cloud homomorphic encryption with splitting key and key delegation can help in meeting healthcare regulatory requirements. The suggested technique is based on FHE algorithm with key delegation to ensure data confidentiality, authentication, integrity, and availability in a multi-level hierarchical order. This will enable the healthcare provider to apply/omit any access rule in any order, especially in medical research environment. <s> BIB001 </s> A Survey on Data Confidentiality and Privacy in Cloud Computing <s> CRITICAL REVIEW OF SOLUTIOS TO DATA CONFIDENTIALITY IN THE CLOUD <s> Cloud computing is an emerging technology which has become today's blistering research area due to the advancement of increased connectivity and it is most interesting and attractable technology which offers the on demand services to the users over the internet. Since Cloud Computing stores the user data and allows the user to work on the cloud system and so the security has become the main concern which creates threat and tries to deploy the Cloud environments. Even though the Cloud Computing is efficient, there are many challenges for data security, which may take away the users from using the cloud computing. To ensure the security of data, we proposed a method by implementing Cramer - Shoup cryptosystem. <s> BIB002 </s> A Survey on Data Confidentiality and Privacy in Cloud Computing <s> CRITICAL REVIEW OF SOLUTIOS TO DATA CONFIDENTIALITY IN THE CLOUD <s> Cloud computing is based on network and computer applications. In cloud data sharing is an important activity. Small, medium, and big organization are use cloud to store their data in minimum rental cost. In present cloud proof their importance in term of resource and network sharing, application sharing and data storage utility. Hence, most of customers want to use cloud facilities and services. So the security is most essential part of customer's point of view as well as vendors. There are several issues that need to be attention with respect to service of data, security or privacy of data and management of data. The security of stored data and information is one of the most crucial problem in cloud computing. Using good protection techniques of access control we can resolved many security problems. Accept that managing privacy and security of information in web highly challenging. This paper describes how to secure data and information in cloud environment in time of data sharing or storing by using our proposed cryptography and steganography technique. <s> BIB003 </s> A Survey on Data Confidentiality and Privacy in Cloud Computing <s> CRITICAL REVIEW OF SOLUTIOS TO DATA CONFIDENTIALITY IN THE CLOUD <s> Individual user and organizations benefit from cloud computing services, which allow permanent online storage of files. The problem occurs when companies store highly confidential documents in cloud servers. Therefore, this paper aims to introduce a backbone structure for a cloud storage system where the security and personal privacy is highly maximized. It is very obvious that cloud computing servers are highly protected against unauthorized access, but in some cases these files stored can be accessible by the maintenance staffs. Fully protection is needed to ensure that the files stored in the server are only accessible to owners. This paper proposes a system that will employ Rivest-Shamir-Adleman (RSA) and Advanced Encryption Standard (AES) combination encryption process using USB device. The files may be accessed in the cloud but all the files will remain encrypted till the USB device is plugged into the computer. The point of applying such method is to fully protect the files and avoid using one single password. The randomly generated passkeys are very complex combinations thus user will not be able to fully memorize them. The proposed system will detect the USB that contains the private-key used for the files to be downloaded from the cloud. <s> BIB004 </s> A Survey on Data Confidentiality and Privacy in Cloud Computing <s> CRITICAL REVIEW OF SOLUTIOS TO DATA CONFIDENTIALITY IN THE CLOUD <s> Cloud computing is a technology or distributed network where user can move their data and any application software on it. But there are some issues in cloud computing, the main one is security because every user store their useful data on the network so they want their data should be protected from any unauthorized access, any changes that is not done on user's behalf. There are different encryption techniques used for security purpose like FDE and FHE. To solve the problem of Key management, Key sharing various schemes have been proposed like third party auditing scheme but it will be failed, if the third party's security is compromised or if the third party is malicious. In this paper, we have used the symmetric key agreement algorithm named Diffie Hellman, it is key exchange algorithm which creates session key between two parties who want to communicate with each other and HMAC for the data integrity and OTP (One Time Password) is created which provides more security. <s> BIB005 </s> A Survey on Data Confidentiality and Privacy in Cloud Computing <s> CRITICAL REVIEW OF SOLUTIOS TO DATA CONFIDENTIALITY IN THE CLOUD <s> Cloud computing is very popular in organizations and institutions because it provides storage and computing services at very low cost. However, it also introduces new challenges for ensuring the confidentiality, integrity and access control of the data. Some approaches are given to ensure these security requirements but they are lacked in some ways such as violation of data confidentiality due to collusion attack and heavy computation (due to large no keys). To address these issues we propose a scheme that uses threshold cryptography in which data owner divides users in groups and gives single key to each user group for decryption of data and, each user in the group shares parts of the key. In this paper, we use capability list to control the access. This scheme not only provides the strong data confidentiality but also reduces the number of keys. <s> BIB006 </s> A Survey on Data Confidentiality and Privacy in Cloud Computing <s> CRITICAL REVIEW OF SOLUTIOS TO DATA CONFIDENTIALITY IN THE CLOUD <s> Cloud computing is a rising technology that is still unclear to many security issues. The most challenging issue today in cloud servers is to ensure data security and privacy of the users. The proposed schema presents HE-RSA or hybrid encryption RSA along with Advanced Encryption Standard or AES to ensure efficiency, consistency and trustworthiness in cloud servers. The goal of this paper is to use various cryptography concepts during communication along with its application in cloud computing and to enhance the security of ciphertext or encrypted data in cloud servers along with minimizing the consumption of time, cost and memory size during encryption and decryption. <s> BIB007
In the study of Pant et al. BIB003 , the data security considerations of Cloud computing are discussed, with an emphasis on the security challenges. The authors proposed a solution to achieve data confidentiality and security in Cloud environments using the Rivest-Shamir-Adleman (RSA) algorithm and a steganography technique. The solution consists of three major steps. The first step is to generate an RSA key, which is created by the user. The data is encrypted using the private key, before it is transmitted over the network. The second step employs a steganography technique to hide the cipher text within an image of any extension, such as a GIF, BMP, or JPEG. The data is stored on a Cloud and hidden in these images. The final step, known as the steganalysis process, uses the steganography tool to extract the cipher text from the image. The benefits of this approach are that only authorised users can access the data. The data is protected on the network as it is encrypted. Furthermore, unauthorized users (intruders) cannot easily detect and uncover the encrypted data, even if the intruder obtains the data accidentally, purposely, or captures it. However, this approach creates a multilevel nature of decryption and encryption, which involves significant computational overhead BIB001 . Additionally, by increasing the size of the data, the time of computation is also increased. Adding an extra layer of security adds more costs in terms of time and efficiency. Another limitation of this solution is that the image extraction software is required on the machine, where the data is accessed; consequently, the availability of data is bound to the availability of that software on the machine. Recently, Raju & Sirajudeen BIB002 presented a solution for data confidentiality to address some challenges of data security. This solution implements the Cramer-Shoup cryptosystem, which is an asymmetric key encryption algorithm, to ensure data security. It comprise three major steps, which are key generation, encryption, and decryption. In the first step, private and public keys are generated. In the second step, data is encrypted and the cipher text is generated, which is then uploaded to the server. The final step includes the decryption of the cipher text, which is done at the receiver's end. The receiver gets the original message if the correct key is provided in the decryption process. The significant advantage of this solution is that data confidentiality is ensured even if the intruder gets access to the data. The risk of unauthorized access to the confidential data and the potential threat of data leakage are eradicated by data encryption. However, the proposed system has been tested with text messages only and does not consider other file formats. On mobile and smart devices, the system running speed could degrade rapidly as decryption occurs at the receiver's end. Moreover, decryption computations could cause battery depletion. Finally, to decrypt the message, a key is provided at the receiver's end, and securing this key is the responsibility of the receiver; thus, the receiver carries the risk of data compromise if the key is lost. Therefore, a new layer or mechanism of security at the receiver's end is required. More recently, Pitchay et al. BIB004 presented a solution to ensure that only the owner of files can access them. Although Cloud solution providers guarantee that the inbuilt security solutions deny all unauthorised access, stored files are still accessible to maintenance staff. Numerous clients are reluctant to store data on Cloud servers, knowing that private or confidential data is accessible by various entities, such as the maintenance staff or the file backup process of the Cloud server providers. The aim of this proposed system was to bridge this gap by applying an advanced level of data protection. The author proposed a hybrid solution that combines both RSA and the Advanced Encryption Standard (AES) in its encryption processes. The proposed system uses a removable device to store the private key, which is used to decrypt and encrypt the data. It is mandatory that, at the time of encrypted data upload process, the removable device is plugged into the system. Furthermore, in the case of requesting back the data from the Cloud to the user's computer, the removable device is again required to download the data. The main advantage of this system is that applying a hybrid encryption method leads to a more complicated encryption algorithm, which results in more difficulties for unauthorised users to break the cipher and access the data. The use of the removable device adds a new security dimension to accessing data from the Cloud. In this respect, this system avoids using a single password; it generates random keys and complex combinations, which makes it almost impossible for intruders to decrypt the data. The limitation of the solution is that users need to keep a backup of the removable device with the key. If the removable device is lost, data cannot be downloaded from the server. This adds overhead to this solution; losing the removable device means the data is lost. More overhead is created when the data is to be accessed by multiple users. The USB drives must be password protected so that, in case it is lost, the data is still secure. Kaur and Wasson BIB005 presented a Cloud data confidentiality technique based on the Diffie-Hellman algorithm. In addition, their proposed solution utilises the Hash Message Authentication Code (HMAC) to ensure data integrity, and a One-Time Password (OTP) to provide more security. The authors suggested that a Fully Homomorphic Encryption (FHE) technique is more effective than full disk encryption. Nevertheless, there are problems with FHE, including key management, key sharing, access control and data aggregation maintenance, all of which reduce the reliability of the scheme. In this paper, a new model is established for key sharing and management in an FHE scheme. The model is based on the fusion of the Diffie-Hellman algorithm and HMAC. In addition, an OTP is created based on a secret key produced by the DiffieHellman algorithm. This algorithm makes a session key between the user and the Cloud, generating a new key between the two every time, before a communication session is started. This algorithm comprises seven steps, beginning with the login and key generation. The third step is the OTP generation, after which the client will enter the operation phase using the HMAC digest, which is the fourth step. After encryption and decryption, users perform data operations. Finally, logout occurs, and the session is closed. Experimental results show that key management time is reduced by establishing a secure channel between the user and the Cloud Service Provider (CSP). This algorithm is reliable and user friendly, as the user does not need to memorise the password to accomplish authentication. It is evident in the literature that encryption is used in numerous solutions to ensure data security in Cloud systems [12 -14] . Thus, it is essential to examine the strengths and weaknesses of these algorithms. An abstract model was presented by Kaur & Wasson BIB005 , which uses a hybrid algorithm called Hybrid Encryption RSA (HE-RSA), which utilises asymmetric key cryptographic RSA and symmetric key cryptographic AES. AES is known to perform better than RSA in terms of time complexity, but secure key distribution and management remain a challenge. HE-RSA aims to enhance the security and improve the efficiency of the original RSA algorithm in terms of time consumption, cost and memory size during encryption and decryption processes. In this scheme, a dual encryption process was established to prevent general attacks against the RSA algorithm, including brute-force, timing and mathematical attacks. In HE-RSA, the probability of failure against attacks will be lowered significantly by the selection of exponents larger than 2048 bits. Moreover, HE-RSA dual encryption protects the transmitted messages against timing attacks and reduces the probability of successful mathematical attacks BIB007 . This algorithm is efficient in handling various types of attacks, such as brute-force, timing and mathematical attacks. The experimental results presented by the authors show that the original RSA has a much higher execution time than that of the proposed HE-RSA algorithm. Since this work is only an abstract model, its efficiency is still yet to be measured at a larger scale by testing it on large Cloud servers. HE-RSA suffers from high key management overhead, because the number of encryption keys is proportional to the number of users. Therefore, with an increase in the number of users, the number of keys also increase, which is an overhead for the company. Saroj et al. BIB006 proposed a scheme to provide strong data confidentiality based on threshold cryptography, while maintaining key management overheads minimal. This scheme consists of three primary objects: the Data Owner (DO), the CSP, and the users. In the beginning, all the users register. The user's credentials are sent to the DO, and then the users are separated into groups by the DO depending on many factors, such as location. Each group has keys for encryption and decryption. Further, the users can authenticate themselves to obtain data from the CSP. The system assumes that the security of the CSP is very high and that the volume of the CSP is very large. The solution utilises a modified Diffie-Hellman algorithm and public key cryptography to maintain secure communication between the CSP and the user. The authors present four algorithms for the proposed scheme. Algorithm 1 is used to ensure that the data communication between the DO and the CSP is secure and that it is used to assure the confidentiality of the DO and the CSP. Algorithm 2 defines the procedure for when a new file is created. Algorithm 3, called the modified Diffie-Hellman algorithm, is used to ensure security in data exchange and communication between the CSP and the user and examines the user's authorisation. Algorithm 4 describes the technique for the threshold cryptography of the user's file. Since data stored in the CSP is encrypted by the DO, only the users and the DO know the encryption key. In addition, the CSP cannot acquire or view client's data. When a user requests data, the CSP sends it to the user in an encrypted form. Hence, the potential for attacks on data during transmission is reduced. However, using many keys affects system performance and requires additional effort to secure them. A system was presented by Han et al. BIB001 that combines Attribute-Based Encryption (ABE) and FHE. This scheme allows users to search for encrypted data without a private key. Two different methods based on different requirements were presented for outsourced data computation. The FHE scheme enhances the capabilities of encrypted data, and the Cloud can perform meaningful computing on the data, primarily in the outsourcing of the data and in searching for encrypted data. The main processes of the proposed systems include key generation, encryption, evaluation, searching, and decryption. The major participants of the system are the DO, a large number of users, clusters of Cloud servers, the key generator of FHE and the attribute authority. The proposed solution is efficient and supports searches for encrypted data, even without a private key. Most other existing solutions that provide searching features for encrypted data are based on bilinear maps and do not support multiple keywords, have poor performance, and are less efficient. Yet, they do not provide a mechanism for key management.