TCC - Engenharia Eletrônica (UACSA)
URI permanente para esta coleçãohttps://arandu.ufrpe.br/handle/123456789/2917
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Item Um estudo sobre ocultação de dados para imagens digitais(2023-04-26) Mendonça, Thatyta de Sousa Silva; Ferreira, Felipe Alberto Barbosa Simão; http://lattes.cnpq.br/9939255113143786; http://lattes.cnpq.br/2783767585088280Digital security is a growing field of study in various areas of science, which includes stega- nography - the art of writing in a hidden manner - as one of the new research areas. This undergraduate thesis presents the implementation of a Least Significant Bit (LSB) steganographic technique to embed text messages in image files. The study is based on literature research on data hiding techniques in digital images and the importance of using watermarking as a measure of protection against piracy and image forgery. The paper presents the theoretical concepts involved in the LSB technique, as well as the methods and tools used for the insertion of the digital watermark. The results obtained from tests conducted prove the effectiveness of the LSB technique in securely and efficiently embedding digital watermarks in digital images.Item Filtragem de sinais sobre grafos aplicada à classificação de dados ruidosos definidos em estruturas irregulares(2023-10-03) Medeiros, Jorge Barros; Ferreira, Felipe Alberto Barbosa Simão; http://lattes.cnpq.br/9939255113143786; http://lattes.cnpq.br/9517722947492097Graph convolutional networks (GCN) allow deep neural networks to learn from data defined in irregular structures represented by a graph. This approach has attracted more and more attention in recent years. Such algorithms generally learn based on the information associated with the vertices and edges present in the graph, being possible to use them to improve the performance of several tasks such as classification of vertices, a signal defined on the graph or the graph itself. The objective of this work is to evaluate the classification of noisy data arranged in an irregular structure from the training of low-pass filters performed by the convolutional layers of a GNN. Filters are designed and applied based on signal processing tools on graphs such as the graph Fourier transform. The graph-based convolutional neural network will perform the learning of parameters for different noise scales in the graph Fourier transform domain that are able to extract relevant information for classification of the noisy dataset.Item Implementação em VHDL e análise comparativa da Transformada Discreta do Cosseno e a aproximação de Lengwehasatit-Ortega(2024-08-27) Silva, Leonardo Nogueira Lindolfo da; Ferreira, Felipe Alberto Barbosa Simão; http://lattes.cnpq.br/9939255113143786; http://lattes.cnpq.br/3309281833356970The high volume of images transmitted daily over the internet consumes a significant portion of bandwidth and processing capacity. To optimize compression and maintain quality, digital signal processing tools like the Discrete Cosine Transform (DCT) are utilized. The DCT is a mathematical operation that concentrates most of the signal's energy in low frequencies, making it highly useful in image compression algorithms. The calculation of the Discrete Cosine Transform is performed using matrix multiplication, where the elements of the transformation matrix are floating-point numbers. To simplify these calculations, various approximations for the Discrete Cosine Transform that use as many integers as possible in their transformation matrices can be found in the literature. Due to the recurrent matrix calculations in modern computational systems, especially for image processing and artificial intelligence, many systems feature ASICs (Application Specific Integrated Circuits) or parts of SoCs (System on Chip) dedicated to this task. In this work, several DCT approximations were evaluated in the context of image compression. The Lengwehasatit-Ortega approximation, which showed the best performance, along with the exact DCT, were implemented in VHDL and synthesized in FPGA. It was observed that, following the same design philosophy, the approximation consumed significantly fewer hardware resources, as expected.Item Projeto de marca d’água digital do tipo frágil para nuvens de pontos 3D baseado em processamento de sinais sobre grafos(2023-09-20) Silva, João Victor da; Ferreira, Felipe Alberto Barbosa Simão; http://lattes.cnpq.br/9939255113143786; https://lattes.cnpq.br/1535688689643312Applications based on 3D models have been constantly gaining prominence due to their higher fidelity and real-world applicability. To achieve this, it is necessary to seek more suitable alternatives for data acquisition, encoding, representation, visualization, and protection. Given the importance of signal processing in preserving the integrity and authenticity of point clouds, there arises a need for advanced approaches that ensure the security and protection of this data. In this context, research and development of a digital watermarking project based on graph signal processing have emerged. This approach aims not only to enhance the protection of this data but also to identify any unwanted and malicious modifications that may occur. To this end, this work presents the creation of a fragile watermarking method for 3D point clouds with the intention of evaluating both its robustness against attacks and its effectiveness. Furthermore, we seek to implement a practical solution that allows the application of this digital watermark directly to 3D point clouds, with the purpose of preserving their integrity and authenticity, protecting them against possible unwanted or malicious modifications. In this way, a literature review is conducted, followed by simulations using databases of real models, using graph signal processing tools (GSP), applying the graph Fourier transform (GFT) technique. The databases used for the simulations were extracted from various research sources, including Oxford RobotCar, KITTI, NuScenes, among others. The metrics responsible for evaluating the performance of the proposed technique are Peak Signal-to-Noise Ratio (PSNR), Root Mean Squared Error (RMSE), and Bit Error Ratio (BER). As a result, it is observed that the proposed digital watermarking method shows satisfactory results in terms of robustness against attacks and preservation of the quality of 3D data. The experiments have demonstrated the feasibility and efficiency of implementing the digital watermark in 3D point clouds. Therefore, it is concluded that the use of a digital watermark based on graph signal processing is a promising solution to ensure the security and authenticity of 3D data in various applications.