# Enhancing Resilience in Digital Twins: ASCON-Based Security Solutions for Industry 4.0
## 3 Proposed Solution
### Ditto Java Base Payload Mapping
While key management holds significant importance in security analysis, it falls outside the scope of this examination. ### Encryption Scheme Overview and Preliminary Assumption

Our proposed communication scheme leverages the ASCON algorithm which is computationally efficient and suitable for resource and power constraints for IoT devices with a 128-bit level of security. ASCON has been evaluated by a number of security experts and has been found to be secure [4]. As long as the security of ASCON is not broken, the proposed scheme with safe implementation is secure. The only information leaked to the adversary is the associated data, namely the thing ID (id). The thing ID is the additional data (or associated data) used in our _authenticated encryption with associated data_ implementation to retrieve the right key upon receiving the message. The thing ID does not provide any advantage to an attacker even if it can be accessed in clear text. In addition, we assume that the private (symmetric) key is deployed before the communication starts through some sort of secure communication channel. Our proposed communication scheme relies on the ASCON algorithm, known for its computational efficiency and suitability for IoT devices operating under resource and power constraints, providing a 128-bit level of security. ASCON's security has been rigorously evaluated and confirmed by security experts [4]. As long as ASCON remains secure, our proposed scheme, when implemented safely, ensures security. The only information accessible to adversaries is the associated data, specifically the _thing ID_. This ID serves as additional data in our _authenticated encryption with associated data_ implementation, facilitating the retrieval of the correct key upon message reception. Even if accessed in plain text, the thing ID does not grant any advantage to an attacker. Furthermore, we presume the private (symmetric) key is securely deployed before communication commences, accomplished through a secure communication channel. #### 6.1.1 Security Aspect of MQTT Protocol

It is important to note that the application protocol used, specifically the MQTT protocol, is not encapsulated or secured using TLS or any other security protocol. As a result, all the metadata associated with the MQTT protocol is openly available to the public, including the topic names, the message payload sizes, and the timestamps of the messages. The MQTT protocol is not designed for secure communication. It is designed for lightweight, efficient communication between constrained devices. Hence, in the proposed scheme, only the message at the application level is secured through the AEAD algorithm and payload encryption. However, one can set up a gateway between the IIoT device and Digital Twin to provide security over the MQTT protocol. _Availability_: Ensure that services remain available to authorized users. 3. **Security Goals**:

_Data Encryption_: Protect data in transit between IoT devices and Digital Twins. _Authentication_: Verify the identity of communicating parties. _Message Integrity_: Detect and prevent tampering with messages. ### Security Analysis of ASCON

ASCON is designed as a lightweight cryptographic algorithm, providing authenticated encryption with associated data (AEAD). Here is a detailed analysis of its security features:

1. **Resistance to Differential Cryptanalysis**:

* _Assumption_: Differential probability \(DP(f,\Delta x\rightarrow\Delta y)\) for an S-box \(f\) is low. * _Proof_: For ASCON, the differential uniformity of the S-box is designed to be low: \[\Pr[f(x)\oplus f(x\oplus\Delta x)=\Delta y]\leq 2^{-d}\] where \(d\) is a small constant, ensuring that differential characteristics are hard to exploit. 2. **Resistance to Linear Cryptanalysis**:

* _Assumption_: Linear probability \(LP(f,\alpha\rightarrow\beta)\) for an S-box \(f\) is low.