Secure and Privacy-preserving Data Sharing in the Cloud based on Lossless Image Coding

Abstract Image and video processing in the encrypted domain has recently emerged as a promising research area to tackle privacy-related data processing issues. In particular, reversible data hiding in the encrypted domain has been suggested as a solution to store and manage digital images securely in the cloud while preserving their confidentiality. However, although efficiency has been claimed with reversible data hiding techniques in encrypted images (RDHEI), reported results show that the cloud service provider cannot add more than 1 bit per pixel (bpp) of additional data to manage stored images. This paper highlights the weakness of RDHEI as a suggested approach for secure and privacy-preserving cloud computing. In particular, we propose a new, simple, and efficient approach that offers the same level of data security and confidentiality in the cloud without the process of reversible data hiding. The proposed idea is to compress the image via a lossless image coder in order to create space before encryption. This space is then filled with a randomly generated sequence and combined with an encrypted version of the compressed bit stream to form a full resolution encrypted image in the pixel domain. The cloud service provider uses the created room in the encrypted image to add additional data and produces an encrypted image containing additional data in a similar fashion. Assessed with the lossless Embedded Block Coding with Optimized Truncation (EBCOT) algorithm on natural images, the proposed scheme has been shown to exceed the capacity of 3 bpp of additional data while maintaining data security and confidentiality

On the Security of a Stream Cipher in Reversible Data Hiding Schemes Operating in the Encrypted Domain

Reversible data hiding in encrypted images has recently emerged as an effective approach to embed and extract a message in the encrypted domain and losslessly recover the host data while maintaining its confidentiality through encryption. That is, the data hider can embed and extract additional data without knowing the image. This approach can be used in cloud applications where the service provider, i.e., the data hider, is not authorized to access the visual content of the host data for security and privacy purposes. Most existing techniques that have been reported in the literature apply a bit-wise encryption method, also known as the stream cipher, prior to data hiding. However, because of the spatial redundancy that characterizes natural images, the security of such an encryption could be compromised. This work is the first one that analyzes reversible data hiding in encrypted images from a security perspective. It proposes a Ciphertext-Only Attack (COA) and highlights the weakness of current state-of-the-art data hiding systems in the encrypted domain. We particularly show how the data hider can break the security of the encryption system and consequently discloses the visual content of encrypted images. Finally, possible solutions to combat COA with existing systems are discussed

Entropy in Dynamic Systems

In order to measure and quantify the complex behavior of real-world systems, either novel mathematical approaches or modifications of classical ones are required to precisely predict, monitor, and control complicated chaotic and stochastic processes. Though the term of entropy comes from Greek and emphasizes its analogy to energy, today, it has wandered to different branches of pure and applied sciences and is understood in a rather rough way, with emphasis placed on the transition from regular to chaotic states, stochastic and deterministic disorder, and uniform and non-uniform distribution or decay of diversity. This collection of papers addresses the notion of entropy in a very broad sense. The presented manuscripts follow from different branches of mathematical/physical sciences, natural/social sciences, and engineering-oriented sciences with emphasis placed on the complexity of dynamical systems. Topics like timing chaos and spatiotemporal chaos, bifurcation, synchronization and anti-synchronization, stability, lumped mass and continuous mechanical systems modeling, novel nonlinear phenomena, and resonances are discussed