###### Abstract
Then, the feature vectors are extracted from these frames using Hahn's discrete orthogonal moments. Next, the extracted feature vectors are binarized and then encrypted based on the proposed 2D chaotic system that is called the modified sine cosine logistic map. Then, a text file containing the encrypted feature vectors is produced. Meanwhile, confidential patient information is stored in another text file, which is combined with the text file containing the encrypted feature vectors in order to generate a single text file. This text file is then converted into a QR code which is encrypted via the proposed chaotic system with the control parameters of this system used as security keys. Finally, the encrypted QR code and the original bio-signal are included in the EPF, which can be safely transmitted through an unsecured communication channel using IoMTs. The analysis of bio-signal security schemes also indicated that most of these schemes are designed to be implemented on personal computers (PCs (laptop or desktop)). However, the use of PCs in the development of solutions in the Internet of Things (IoT) presents some major drawbacks, namely: (i) the large size and weight of the PCs, which limits their portability. As a result, PC-based applications are rarely deployed in IoTs [29; 30]. (ii) In addition, PCs are expensive in terms of energy consumption, especially if they are used for long periods, which reduces their energy efficiency. (iii) Furthermore, PCs are generally costly, which limits their use in IoT-based projects and smart cities that require low-cost solutions [31]. To overcome these limitations, the proposed security scheme was implemented on a Raspberry Pi-embedded board, which is considered as one of the most appropriate hardware for IoMTs applications [32]. In fact, Raspberry Pi boards offer the following benefits: (i) low cost and (ii) reduced dimensions, since the average dimensions of various Raspberry Pi models are 85.60 mm (length) \(\times\) 56.5 mm (width) \(\times\) 17 mm (height). Therefore, these boards are desirable for their portability. In addition, (iii) Raspberry Pi boards are widely appreciated for their low power consumption. Indeed, Raspberry Pi 4 model B consumes between 3.8 W and 6.0 W. This makes Raspberry Pi boards efficient in terms of energy consumption. (iv) Furthermore, parallel computing is an extra advantage offered by Raspberry Pi boards. This advantage can be used to considerably accelerate the execution time of applications that are designed to run in parallel [33]. We can summarize the main contributions of our work as follows:  
1. Proposing a new 2D chaotic system based on the existing modified logistic map and then demonstrating the chaotic behavior of the proposed system. 2. Proposing a new security system to protect the confidentiality of electronic patient data (bio-signal records and patient personal information) in IoMTs. 3. Implementing the proposed security system on a Raspberry Pi board to take advantage of its multiple benefits (low cost, multi-core for parallel computing, low power consumption, portability, etc.). 4. Providing simulation and comparison results on a PC and a Raspberry Pi 4 Model B-embedded board to confirm the good robustness and the cost efficiency of the proposed system in IoMTs. The rest of this work is organized in the following manner. In the second section, we outline the preliminaries employed within our work. The third section deals with the proposed two-dimensional sine cosine chaotic map. The fourth section describes the proposed security scheme for bio-signals and patient data privacy preservation. The fifth section outlines details on the proposed rapid implementation of our scheme on Raspberry Pi. Simulation results and comparisons are discussed in the sixth section. Finally, conclusions and future work are given in the last section.