# Enhancing Resilience in Digital Twins: ASCON-Based Security Solutions for Industry 4.0
## 2 Literature Review  
This section comprehensively reviews the existing literature, encompassing academic research, industry reports, and practical implementations of secure communication between DTs and resource-constrained IoT devices. In our previous SLR work [5], we analyzed a wide array of studies and publications to understand the current state of knowledge in this domain comprehensively. A critical aspect of our literature review involves assessing existing solutions and technologies utilized in practice. We evaluated these solutions' effectiveness, limitations, and real-world applicability in protecting the communication pathways between Digital Twins and IoT devices with limited resources. Based on our thorough literature review, we clearly articulated the specific research objectives and questions that our paper aims to address. These objectives guided our exploration of novel approaches and the development of a lightweight cryptographic solution tailored to the needs of this emerging field. It is crucial to establish secure communication between the physical and digital components to maintain the reliability and security of Digital-Twin-based systems. These physical IoT components' computational, power, and storage limitations must be considered. In this context, we examined 14 papers that explore data confidentiality, integrity, and privacy within the Digital Twin ecosystem. Table 1 summarizes the security measures utilized in the literature. \begin{table}
\begin{tabular}{l l l} \hline \hline
**Ref.** & **Security Mechanism(s)** & **Goal(s)** \\ \hline
[6] & Central access control system based on OAuth and XACML & Secure access control \\ \hline
[7] & Anonymous communication based on secret handshake scheme and group signature & Unforgeability and conditional traceability (privacy) \\ \hline
[8] & Differential privacy techniques & Privacy and confidentiality of data \\ \hline
[9] & Blockchain and Smart contract-based & Validate the legitimacy and integrity of data collected from \\  & Proof-of-Authentication (PoA) & Industrial Internet of Things nodes. \\ \hline
[10] & Blockchain, Smart contract, and Deep learning & Integrity of data, detect botnet behavior \\ \hline
[11] & Quantum communication technologies & Improve overall security of communication between DT and IIoT \\ \hline
[12] & Trusted Execution Environment and Unclonable Functions (PUFs) & Security and Trustworthiness of communication \\ \hline
[13] & Attribute-based Access Control & Secure data storage \\ \hline
[14] & Blockchain & Authentic data generated from clusters before they are used in DT \\ \hline
[15] & Authorization Blockchain and Storage Blockchain & Secure data sharing through authorization \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Security Mechanisms for Securing Data in DT and Industrial Internet of Things Communication [5]. To address security challenges like communication trust and privacy protection, the authors in [7] introduced a robust framework for secure vehicular digital twin communication. This framework leveraged anonymous authentication as a key component. The specific authentication protocol was introduced by the authors, relying on a secret handshake scheme and group signature to accomplish the goal. This approach effectively addressed issues related to the authenticity of messages and conditional traceability. The proposed framework established secure communication channels not only between iTwins (Digital Twins) and their physical counterparts but also among iTwins themselves.The preservation of data confidentiality and integrity during transmission was a primary focus. To address the challenges of data volume, unreliable communication channels, and security threats in Industrial IoT (IIoT), the authors in [9] proposed an integrated framework that combines blockchain and Deep Learning (DL). This framework introduces a new DT model for simulating security-critical IIoT processes and employs blockchain-based data transmission with smart contracts to ensure data integrity.