Quick Response (QR) two-dimensional codes were designed to send information in a simple and versatile way, such as sharing a product or company website. Nowadays they can be found in documents with sensitive information, such as personal documents (passports, visas, bank transfers) and documents with restricted information of companies (financial reports, legal documents), for this reason it is important to take care of the information that is sent or shared, depending on its use, it is important to add levels of security to the information encoded in QR codes, since in some cases sensitive information is sent. In this paper we propose to add two levels of security to QR codes that will share sensitive information. A first level of security is the encryption of the original information through the Privacy Guard (GPG) method, a second level of security is the multiplexing of two pieces of information in a chromatic QR code, where each color represents an encoded information, the incorporation of the two levels of security will keep the information shared by the users secure.

QR codes (Quick Response) were originally developed by the automotive industry to enable rapid data exchange and have since evolved into versatile tools for commercial applications, such as linking to products or websites. However, the scope of their adoption has expanded into sensitive domains including financial, corporate, and governmental sectors. In order to address increasing security concerns, this work proposes a novel three-layer protection scheme. First, data confidentiality is ensured through encryption—in this study, symmetric AES (Advanced Encryption Standard) encryption is used as an example, though any encryption algorithm can be employed. Second, a multiplexing technique is employed to integrate two independent dichromatic QR codes into a single printed chromatic structure. Third, the recovery of each dichromatic code is achieved through the controlled incidence of specific wavelengths, not only providing improved channel separation but also functioning as a physical access control mechanism. This physical layer restricts unauthorized reading.

A synchronous-Buck converter is proposed as part of a maximum power point tracking (MPPT) controller for charging a 12 V battery from a photovoltaic (PV) solar panel. This design incorporates a control module that manages energy flow from the solar panel to the battery. The novel module sequentially integrates MPPT, active current limiting (constant current, CC), and voltage regulation (constant voltage, CV), along with protection mechanisms and low-computational-complexity control. It also incorporates a synchronous-Buck converter with a current PI control loop; this differs from the strategy used in a traditional Buck converter in terms of how much switching losses are reduced. The proposal integrates these two stages and establishes a robust control scheme that enables the battery charging process in photovoltaic systems to adapt to variations in both input and output conditions. Additionally, an irradiance detection logic has been incorporated to ensure that the system operates only when there is sufficient solar radiation is available, thereby extending the system’s lifetime and improving overall energy utilization. This work focuses on the practical integration and experimental validation of a comprehensive maximum-power-point-tracking (MPPT)-based charging system. The main contributions of this study can be summarized as follows: (1) practical integration; (2) experimental validation; (3) hardware-based protection strategy and low-computational-complexity control. To validate the designed system, a 70 W prototype with 90% efficiency was implemented and tested. The experimental results verify that the implemented protection mechanism prevents the battery from discharging unnecessarily during low-irradiance or nighttime conditions. This improves the overall efficiency of the system and extends the battery’s lifetime.

The counterfeiting of official documents and banknotes represents a critical threat to global security and requires robust and low-cost protection techniques. This work presents an innovative information security system that uses photoluminescent inks for chromatic multiplexing of QR codes. Unlike conventional cryptographic methods, the proposed approach employs physical-layer information hiding through the superposition of two QR codes encoded in magenta and cyan colors on a white background. The controlled interaction between these codes generates an additional logical state that enables a third representation of information through pixel-level operations. The resulting chromatic QR code remains visually imperceptible under ambient illumination and can be reliably recovered through chromatic demultiplexing and thresholding process. Additionally, its visibility can be enhanced under ultraviolet (UV) excitation due to photoluminescent behavior and spectral response variations. The experimental results demonstrate that both encoded data layers can be extracted independently with high fidelity using standard CMOS sensors, while preserving structural integrity and decodability. The proposed scheme increases information density within a single optical tag while improving resistance against unauthorized replication and visual forgery.