# Enhancing Communication Security in Drones Using QRNG in Frequency Hopping Spread Spectrum
## 1 Introduction  
In an increasingly digital and interconnected world, and with the advent of sophisticated AI techniques [1], the need for secure communication channels has never been more critical. Sensitive information, whether personal, corporate, or governmental, must be protected against a myriad of threats including eavesdropping, data interception, and deliberate jamming. Frequency Hopping Spread Spectrum (FHSS) [2; 3] has long been employed as a technique to enhance the security and robustness of wireless communications.  
The ever-increasing demand for secure communication channels has led to the exploration of advanced techniques that can withstand interception and jamming attempts. Frequency Hopping Spread Spectrum (FHSS) is a well-established method to enhance communication security. This article explores the potential of using a Randomness Processing Unit (RPU) to generate true random sequences for frequency hopping, thereby significantly enhancing the unpredictability and robustness of communication systems. By rapidly changing the carrier frequency according to a specific sequence, FHSS spreads the signal over a wide spectrum, making it more resistant to interference and more difficult to intercept.  
Traditionally, the sequences used for frequency hopping are generated using pseudo-random number generators (PRNGs). While these sequences can appear random, they are ultimately deterministic and, given enough time and resources, can potentially be predicted or reverse-engineered. This inherent vulnerability poses a significant risk to communication systems, especially in environments where security is paramount. Improvements over traditional PRNGs [4; 5; 6] have been explored in the literature, with emphasis on an efficient implementation and portability.  
The advent of Randomness Processing Units (RPUs) [7; 8] offers a promising solution to this challenge. RPUs are specialized hardware devices capable of generating true random numbers based on inherently unpredictable physical processes, such as quantum noise or thermal fluctuations. Unlike PRNGs, the numbers generated by RPUs are not reproducible or predictable, even with complete knowledge of the system's internal workings.  
This manuscript explores the concept of leveraging RPUs to generate true random sequences [9; 10] for frequency hopping in communication systems. By replacing deterministic sequences with truly random ones, we can significantly enhance the security and robustness of FHSS. We will study the theoretical background of FHSS, the mathematical formulation of true random frequency hopping, and the security benefits and implementation challenges associated with this approach. A preliminary use case with an actual QRNG device setup in a multi-drone configuration is presented. This exploration aims to highlight the importance of incorporating true randomness in securing modern communication infrastructures.  
The paper is organized as follows: Section 2 provides an overview and related works while Section 3 provides the theoretical background and considerations for Frequency Hopping Spread Spectrum (FHSS) and the use of Randomness Processing Units (RPUs). In Section 4, we present our methodology for integrating an RPU to generate truly random frequency hopping sequences, enhancing the security of FHSS systems. Section 5 details the implementation aspects, including the setup of the RPU, generation and synchronization of frequency hopping sequences, and security protocols. In Section 6, we apply the proposed method to a drone cloud with a ring topology, demonstrating its benefits in multi-drone communications. Section 7 presents the evaluations, including experimental setup, procedures, and results that demonstrate the effectiveness of our approach. Section 8 explores practical applications and potential future developments of the system. Finally, Section 9 concludes the paper and outlines future research directions.