# RACHEM: Reinforced Reliable Computing in Cloud by Ensuring Restricted Access Control
## 2 Literature Survey
### Cloud Security Using Access Control Schemes  
The cloud computing framework employs RBAC and ABAC policies to regulate identity and access management. The key features of RBAC include the assignment of roles to authorized cloud services, validation of user role credentials, and management of service transactions based on rules defined in the ACL. The primary objective of the ABAC policy is to prevent unauthorized users from accessing the network, user data, and IT resources. ABAC enforces restrictions on unauthorized access by implementing comprehensive IAM constraints. The customization enabled by ABAC allows administrators to modify and adjust access control rules to align with the specific needs of the organization [60]. The rapid growth and widespread adoption of cloud computing in recent years has underscored the need for models that ensure secure access rights in the cloud environment [61; 62]. Conventional encryption models often do not address access rights based on user roles or assigned functionalities [63]. Therefore, enforcing restricted access policies in cloud environments is essential for maintaining data confidentiality [64]. A notable approach involves integrating cryptographic schemes with access control mechanisms. In the RBAC model, a role represents an authorized set of permissions assigned to a user for performing specific tasks within a computing domain [65]. User requests are processed following a critical evaluation. Authenticated users become participants in the ACL and are granted a secret key to access public data when an appropriate role is assigned. An administrative entity, referred to as the role manager, oversees the relationships between roles (role \(\rightarrow\) role) and between roles and users (role \(\rightarrow\) user). The role manager first validates a user's eligibility for a specific role, then monitors the role parameters to ensure compliance with membership requirements and evaluates the hierarchical relationships among roles. For each role-to-user mapping, role parameters are updated within the cloud domain. To protect sensitive data, the data owner encrypts the information, and only authorized roles are permitted to decrypt the file using a secret key. This mechanism is referred to as Role-Based Encryption (RBE) [66]. Although various access control approaches, such as those proposed in [67; 32; 68], provide defensive measures against malicious activities, they do not directly address methods for mitigating cloud-specific attacks. The RBAC model was initially introduced in [69] and subsequently enhanced in studies such as [70; 71; 72; 73]. Given that hierarchical structures effectively model access control, a hierarchical cryptographic scheme was proposed in [74] to represent access control mechanisms. The challenges associated with outsourcing cryptographic access control policies were first discussed in [75]. Subsequently, several schemes were introduced in [76; 77; 78], presenting cost-effective approaches to access control. To incorporate identity-based validation, a hierarchical identity-based encryption (HIBE) scheme was proposed in [79; 80; 81], emphasizing that only users within a predefined hierarchical tree structure have the right to decrypt encrypted messages. Users outside this hierarchy are denied access. An improved HIBE scheme was later introduced in [82] to address the bottleneck of identity validation through private key generation. However, this approach was vulnerable to single-point failure if the integrity of the root private key generator was compromised. Consequently, there has been a significant shift from traditional access control mechanisms towards Hierarchical Key Management (HKM), as discussed in [83]. An integrated approach for assessing the vulnerability of an Industrial Control System and protecting the system from cyber-physical attacks was proposed in [84]. However, the work did not present a mitigation scheme and risk analysis if the integrity of the computingsystem itself has been compromised.