# Prototyping the Symmetry-Based Chaotic Communication System Using Microcontroller Unit
## 1 Introduction
[PERSON] [20] used Arduino Uno and a wireless SX LoRa-1278 module to securely transfer temperature sensor data using master and slave chaotic systems synchronized with both the proportional-derivative (PD) controller and the quasi-sliding mode controller (QSMC). [PERSON] et al. [21] proposed a real-time chaotic communication system based on Arduino and a Bluetooth wireless protocol. To synchronize Chen maps in the transmitter and receiver, a model-matching control was used, and chaos was applied to generate, encode, and decode a binary signal key. Meanwhile, the experimental data on properties of such communication systems, e.g., transfer rate and bit-error-rate (BER) at different signal-to-noise ratio (SNR) values, as well as a numerical evaluation of the security level, are often omitted in the literature. One can find relatively different quantitative estimations in papers on FPGA-based CCSs. In particular, [PERSON] and [PERSON] [22] defined the throughput of the communication system based on synchronized Rossler oscillators as 2850 Mbps. In the work by [PERSON] et al. [23], the data rate achievable for a CSK-family CCS with a 50 MHz clock and 8196 samples per symbol was 6.1 kbps. In terms of the transfer rate, MCU-based systems should be significantly inferior. However, properties such as noise immunity and transmission secrecy could be relevantly evaluated only in real hardware experiments, which is a key motivation for this paper. Thus, the main contribution of the current study is as follows:  
1. We consider a coherent chaos-based communication system with symmetry coefficient modulation (SCM), a novel technique that exploits the properties of the symmetric numerical integration used to generate a discrete chaotic map from a continuous system. The classical Lorenz system was chosen as a continuous prototype due to its well-known chaotic properties. We studied the proposed CCS in both simulation and hardware implementation based on the Arduino platform. 2. The possibility of data transfer using symmetry modulation is shown experimentally. Several important properties of the system, such as noise resistivity and secrecy,were evaluated in comparison with parameter modulation (PM) implemented in the same hardware. 3. We discovered that, while possessing approximately the same noise resistivity, symmetry modulation has a greater secrecy than PM in the experimental setup. A quantified return map analysis (QRMA) technique was used to evaluate the secrecy of the communication system. The rest of the paper is organized as follows: in Section 2, the investigated chaotic system and the applied numerical method are given. Then, the architecture of the developed chaos-based communication system is described, including two considered modulation techniques: symmetry-based and parameter-based modulation. The experimental setup is shown. Section 3 presents the results of the experimental investigation of the designed CCS prototype. Section 4 discusses some practical implementation issues that appeared during this study, and Section 5 concludes the paper.