Academic literature on the topic 'Image Encryption'

In this thesis we present an overview of sparse approximations of grey level images. The sparse representations are realized by classic, Matching Pursuit (MP) based, greedy selection strategies. One such technique, termed Orthogonal Matching Pursuit (OMP), is shown to be suitable for producing sparse approximations of images, if they are processed in small blocks. When the blocks are enlarged, the proposed Self Projected Matching Pursuit (SPMP) algorithm, successfully renders equivalent results to OMP. A simple coding algorithm is then proposed to store these sparse approximations. This is shown, under certain conditions, to be competitive with JPEG2000 image compression standard. An application termed image folding, which partially secures the approximated images is then proposed. This is extended to produce a self contained folded image, containing all the information required to perform image recovery. Finally a modified OMP selection technique is applied to produce sparse approximations of Red Green Blue (RGB) images. These RGB approximations are then folded with the self contained approach.

In this study, a new method is proposed to protect JPEG still images through encryption by employing integer-to-integer transforms and frequency domain scrambling in DCT channels. Different from existing methods in the literature, the encrypted image can be further compressed, i.e. transcoded, after the encryption. The method provides selective encryption/security level with the adjustment of its parameters. The encryption method is tested with various images and compared with the methods in the literature in terms of scrambling performance, bandwidth expansion, key size and security. Furthermore this method is applied to the H.263 video sequences for the encryption of I-frames.

Security and privacy of photos stored in the clear in third party servers has been the biggest concern for customers in recent years. One way of enhancing the privacy and security of photos stored in third party servers is to encrypt the photos before storing them. However, using encryption to secure the information held in the photos precludes applying any image processing operations while they are held in the third party servers. To address this issue, we have designed and implemented a distributed image storage system that is based on the Chord protocol which enhances privacy using chaotic map transformations and image segmentation. The distributed system we use has two types of resources: trusted server resources and untrusted peer-to-peer resources. The images are encrypted using an Arnold's cat map algorithm and split into strips before uploaded to the destination machines. The cat map algorithm shuffles an image pixels and produces a noise-like image. A pixelated (a group of nearby pixels are made the same color) image of the original image is generated to represent it in the central server. From the pixelated image we generate the key parameters that control the cat map transformations. A variety of pixel-level, block-level and binary filters have been implemented to support image processing on encrypted images in the system. One of the concerns of using cat maps for security purposes is the quality of shuffling provided by these transformations. For certain parameter values and image sizes cat map transformations reveal the original image as ghosts or clusters. As part of my thesis, I studied the ghost and cluster formation scenarios. I performed many experiments and proposed simple tests that can be used to detect the parameter values that should be avoided.<br>La sécurité et l'intimité des images électronique stockée dans des serveurs tierces est une des plus grandes préoccupations de nos jours. L'une des manières d'améliorée la sécurité est de crypter les données contenu dans les images avant de les télécharger vers le serveur en question. Cependant, le fait d'utiliser des techniques cryptographiques pour assurer la sécurité des images, ce la empêche l'application d'opérations de traitement d'images pendant qu'ils résident sur les serveurs. Pour résoudre ce problème, nous avons conçu et mis en œuvre un système distribué pour télécharger les images sur les serveurs qui est basée sur le protocole "Chord", améliorant la sécurité en utilisant des techniques de la théorie du chaos pour transformer l'image puis finalement la segmenter. Le système distribué que nous utilisons contient deux types de ressources : des ressources de serveur fiable et des ressources non fiables paires à pair. Les images sont cryptées avec l'application de l'algorithme chat d'Arnold, l'image résultante est divisée en morceaux avant d'être télécharger aux machines destinataires. L'algorithme de chat d'Arnold produit une image bruyante. Une image pixélisé (un groupe de pixels voisines sont changer de façon que les couleurs soient les même entre eux) est aussi créé de l'image originale. L'image pixélisée est utilisé pour représenter l'image originale sur le serveur central. A partir de l'image pixélisée, nous créerons les paramètres de la clé qui contrôlent la transformation chaotique. Une variété de filtres au niveau des pixels, blocs des pixels et de la représentation binaire ont été mis en œuvre pour permettre des opérations de traitement sur les images cryptées dans le système. La qualité du brouillement en utilisant les transformations chaotiques est un souci par rapport à la sécurité. Pour certaines valeurs de paramètres et dimensions d'images, on peut percevoir des fantômes de l'image originale. Pour ma thèse de maitrise, J'ai étudié les scenarios qui donnent naissance à des formations de fantômes. J'ai effectué de nombreuses méthodes expérimentales et proposer des simples testes pour pouvoir détecter les valeurs de paramètres qui doivent être évité.

The digital watermarking technique embeds meaningful information into one or more watermark images hidden in one image, in which it is known as a secret carrier. It is difficult for a hacker to extract or remove any hidden watermark from an image, and especially to crack so called digital watermark. The combination of digital watermarking technique and traditional image encryption technique is able to greatly improve anti-hacking capability, which suggests it is a good method for keeping the integrity of the original image. The research works contained in this thesis include: (1)A literature review the hyperchaotic watermarking technique is relatively more advantageous, and becomes the main subject in this programme. (2)The theoretical foundation of watermarking technologies, including the human visual system (HVS), the colour space transform, discrete wavelet transform (DWT), the main watermark embedding algorithms, and the mainstream methods for improving watermark robustness and for evaluating watermark embedding performance. (3) The devised hyperchaotic scrambling technique it has been applied to colour image watermark that helps to improve the image encryption and anti-cracking capabilities. The experiments in this research prove the robustness and some other advantages of the invented technique. This thesis focuses on combining the chaotic scrambling and wavelet watermark embedding to achieve a hyperchaotic digital watermark to encrypt digital products, with the human visual system (HVS) and other factors taken into account. This research is of significant importance and has industrial application value.