# RACHEM: Reinforced Reliable Computing in Cloud by Ensuring Restricted Access Control
### Motivation  
The foundation of cloud computing lies in the collaborative integration of advanced technologies to foster innovation, enhance server interaction, and overcome the inherent limitations of distributed cloud infrastructure. However, increased server interaction often results in heightened risk of service abuse. The presence of multiple abstraction layers within cloud architectures significantly expands the system's vulnerability surface. Additionally, establishing trust between stakeholders--particularly in the formulation and enforcement of SLAs--remains a persistent challenge. Insecure computing interfaces can compromise data confidentiality, integrity, and accountability, placing a critical responsibility on service providers to ensure secure access platforms. The Application Programming Interface (API) plays a central role in enabling interaction and communication within cloud environments. APIs offer mechanisms for encryption, authentication, and activity monitoring. However, these mechanisms can be susceptible to malicious exploitation, especially in the presence of weak API security configurations. Furthermore, multitenancy--wherein multiple users share the same infrastructure--is a key contributor to increased vulnerabilities, broader attack surfaces, and higher instances of cloud exploitation [3; 7; 8; 9]. Existing cryptographic systems have proven insufficient in enforcing robust privileged access control mechanisms [22; 23; 24; 25; 26; 27; 28]. Traditional access control models, such as RBAC and Attribute-Based Access Control (ABAC), have demonstrated effectiveness in defining restricted access. However, they often fall short in delivering flexible access management and real-time identity validation, particularly in scenarios that demand dynamic updates during role allocation or revocation [10; 29; 30]. Traditional RBAC models are constrained by static role assignments, limiting their effectiveness in dynamic, multi-tenant cloud environments where user roles and access privileges change frequently. This inflexibility introduces considerable administrative overhead, as manual updates to role hierarchies and permissions are required to reflect contextual and user-specific changes. Such processes are time-consuming, prone to errors, and hinder system scalability, increasing the risk of misconfigurations and unauthorized access. These limitations highlight the necessity for adaptive and automated access control mechanisms, integrated with cryptographic techniques such as partial homomorphic encryption, to enhance both security and scalability. ABAC allows access decisions based on user and resource attributes. However, if the number of attributes increases, the performance overhead and complexity of the computing domain also increases. To overcome these limitations and to strengthen the IAM policies, business enterprises can investigate innovative and novel approaches like establishing dynamic authorization frameworks that permit the evaluation of access policies in real-time based on user attributes. One approach would be to implement constant monitoring and enable adaptive access control mechanisms based on user attributes that can dynamically adjust permissions based on evolving risk profiles. Service users are often skeptical regarding the privacy and security concerns needed to safeguard their data in the computing domain. This, mistrust further raises concerns regarding severe cloud attacks, and persistent threats facilitated by the means of phishing, the introduction of malware, hacked third-party networks, and direct attacks [31]. Someadditional threats to cloud security encompass direct attacks, potential loss of data, and the inability of the administrator to determine the extent of attacks. The untrusted service nodes tend to increase the overhead and complexity of a Trust Management System (TMS) and introduce security threats like collusion attacks, DoS attacks, Sybil attacks, and on-off attacks [32; 33; 34; 35; 36]. The collusion attack is an extremely common type of security attack.