# Secured Real-Time Machine Communication Protocol
## 1 Introduction  
Industrial communication protocols are fundamental to ensuring the reliable and efficient transfer of data in industrial networks. These protocols are designed to operate across different layers of the TCP/IP model, with each layer contributing unique features that collectively shape the functionality, performance, and security of industrial communication systems. From the physical layer to the application layer, these protocols underpin critical operations in manufacturing, process automation, and resource management. However, their inherent features and limitations often pose challenges when adapting to the increasing complexity and demands of modern industrial environments. With the advent of Industry 4.0, characterized by the integration of IoT devices, massive datasets, real-time analytics, and artificial intelligence-driven decision-making, traditional communication protocols often struggle to meet the stringent requirements for performance, scalability, and security [1]. The interconnected nature of Industry 4.0 systems exposes networks to new vulnerabilities, such as cyber attacks, unauthorized access, and data breaches, necessitating the development of communication protocols that are not only efficient but also resilient against these threats. Moreover, the increasing adoption of post-quantum technologies introduces additional requirements for cryptographic robustness to ensure long-term security in the face of advancing quantum computing capabilities [2]. To address these challenges, we introduce a novel industrial communication protocol named the Secure Real-Time Machine Communication Protocol (SRMCP). SRMCP is a cross-layer protocol that spans from the data-link layer to the application layer, integrating advanced security measures while maintaining the performance requirements ofindustrial applications. The security architecture of SRMCP incorporates widely accepted cryptographic techniques, including asymmetric and symmetric encryption standards. For example, the Diffie-Hellman Key Exchange Agreement (DH-KEA) [3] and the Kyber Key Encapsulation Mechanism (Kyber-KEM) [4] are utilized for secure key exchange, while the Advanced Encryption Standard in Galois Counter Mode (AES-GCM) provides robust encryption suitable for post-quantum environments [5]. In addition to its robust cryptographic framework, SRMCP introduces an innovative mechanism called \"Port Hopping\". Inspired by Frequency Hopping Spread Spectrum (FHSS) techniques [6], which distribute signals across multiple frequency channels to enhance security and reliability, \"Port Hopping\" disperses data transmission across a wide range of TCP/IP sockets. This approach not only disguises traffic patterns but also makes it exceedingly difficult for adversaries employing Deep Packet Inspection (DPI) or machine learning algorithms to identify or compromise the communication stream. The protocol ensures seamless reassembly of data on the client side, thereby preserving transaction integrity while significantly enhancing resilience against traffic analysis attacks. In summary, the proposed SRMCP protocol brings the following contributions:  
1. **Design of SRMCP:** A novel industrial communication protocol that integrates post-quantum cryptographic techniques such as the Kyber Key Encapsulation Mechanism (Kyber-KEM) and AES-GCM encryption, providing robust security against emerging quantum computing threats. 2. **Introduction of Port Hopping:** Inspired by frequency hopping in wireless communications, this mechanism significantly enhances security by distributing communication across multiple TCP/IP sockets, obfuscating traffic patterns, and mitigating risks from advanced traffic analysis techniques. 3. **Real-Time Transaction Mechanism:** A robust transaction mechanism ensures compliance with IEC 61131 standards for real-time systems, as well as addressing challenges such as resource management and memory leak prevention. 4.