# RACHEM: Reinforced Reliable Computing in Cloud by Ensuring Restricted Access Control
## 2 Literature Survey
### Algorithmic Procedure for RACHEIM
The evaluation considers key performance metrics including encryption time, decryption time, ciphertext size, and key size across a range of standardized configurations. \begin{table}
\begin{tabular}{p{56.9 pt} p{56.9 pt} p{56.9 pt} p{56.9 pt}} \hline \hline
**Threat Category (STRIDE)** & **Potential Attack Scenario** & \begin{tabular}{c} **Mitigation** \\ **Strategy Proposed** \\ **in** \\ **RACHEIM** \\ \end{tabular} & \begin{tabular}{c} **Security** \\ **Mechanism** \\ **Employed** \\ \end{tabular} \\ \hline Repudiation & \begin{tabular}{c} Malicious user \\ denies initiating or \\ performing an \\ action. \\ \end{tabular} & \begin{tabular}{c} All user role \\ transactions are \\ logged and verified \\ against \\ time-stamped \\ request tokens and \\ identity credentials. \\ \end{tabular} & \begin{tabular}{c} Immutable logging \\ and authenticated \\ role-token \\ validation. \\ \end{tabular} \\ \hline Information Disclosure & \begin{tabular}{c} Exposure of \\ sensitive data to \\ unauthorized users \\ or CSP. \\ \end{tabular} & \begin{tabular}{c} Encrypted data and \\ role-based \\ decryption keys \\ prevent CSP or \\ unauthorized roles \\ from accessing \\ content. \\ \end{tabular} & \begin{tabular}{c} Encrypted data and \\ Encryption with \\ hidden content \\ from CSP; \\ role-bound \\ decryption. \\ \end{tabular} \\ \hline Denial-of-Service (DoS) & \begin{tabular}{c} Overloading the \\ system with invalid \\ or excessive \\ requests. \\ \end{tabular} & \begin{tabular}{c} Requests are \\ validated in two \\ checkpoints: \\ identity-role \\ mapping and \\ privilege validation \\ before execution. \\ \end{tabular} & \begin{tabular}{c} Request throttling \\ and dual-stage \\ access validation \\ mechanism. \\ \end{tabular} \\ \hline \multirow{4}{*}{Escalation of Privileges} & \begin{tabular}{c} Unauthorized user \\ tries to perform \\ privileged \\ operations. \\ \end{tabular} & \
\begin{tabular}{c} Access is restricted \\ based on \\ hierarchical role \\ parameters and \\ identity checks; \\ revoked roles \\ cannot regain \\ privileges. \\ \end{tabular} &
\begin{tabular}{c} Hierarchical \\ role-based access \\ control (RBAC) \\ with dynamic \\ revocation support. \\ \end{tabular} \\ \hline \hline \end{tabular}
\end{table} 
Table 3: _Cont._Each data point presented in Figures 5a,b and 6a,b represents the mean of 30 independent simulation runs, all conducted under identical experimental conditions to ensure statistical reliability and minimize the influence of transient system load or random noise. The error bars included in the simulation plots represent \(\pm 1\) standard deviation and 95% confidence intervals, offering a statistically sound summary of performance variability. This statistical treatment affirms the improvements achieved by the proposed RACHEIM model in both encryption and decryption times when compared with baseline homomorphic encryption schemes. Figure 5a,b present a comparative analysis of encryption and decryption times, respectively, with varying key sizes and fixed data sizes. As shown in Figure 5a, when the key size increases from 512 bits to 2048 bits, the RACHEIM model achieves a 20% reduction in encryption time compared to the RSA multiplicative homomorphic encryption scheme and a 40% reduction relative to the Paillier additive homomorphic encryption scheme. Similarly, Figure 5b demonstrates that for key sizes up to 1024 bits, RACHEIM exhibits a 15% reduction in decryption time compared to the RSA multiplicative scheme and a 20% reduction compared to the Paillier additive scheme. These results clearly indicate the computational efficiency and performance advantage of the RACHEIM model under varying cryptographic configurations.