The secrecy of various forms of multimedia data constitutes a significant aspect of the cybersecurity field. In this case, chaos-based image ciphers can be adapted. Chaotic image encryption has been investigated in th...
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The secrecy of various forms of multimedia data constitutes a significant aspect of the cybersecurity field. In this case, chaos-based image ciphers can be adapted. Chaotic image encryption has been investigated in the literature using different transformation domains, such as spatial, discrete Fourier transform, wavelettransform, etc. Although some frequency-based cryptosystems exhibit favorable confusion properties, they may suffer in terms of diffusion properties and fail in terms of some statistical characteristics, which make them vulnerable to various statistical, analytical, and differential attacks. In this regard, we adopt a dual-domain (wavelet and spatial domains) image cryptosystem and propose a novel diffusion process in the wavelet domain to address the problem of weak resilience against the aforementioned attacks. The proposed diffusion process in the wavelet domain is applied only on 1/16 of the pixels of the plain image, which makes it computationally more efficient compared to the existing wavelet domain-based works. In addition, the proposed cryptosystem solves the bell shape histogram problem associated with some frequency-based cryptosystems, which has been verified using different performance metrics in our simulation results. We also introduce a novel key-dependent chaotic variable generator to generate the required initial conditions and control parameters for the adopted enhanced chaotic map. The superiority of the proposed algorithm compared to some of the existing state-of-the-art has been verified through various performance metrics. These include different types of correlation coefficients, histogram visualization, histogram deviation, irregular deviation, mean square error, chi-square test, entropy test, and differential analysis.
Despite the approval of a new standard in 2009, JPEG-extended range lossless, current digital products still employ previous standards for lossless image compression, such as JPEG, JPEG2000, JPEG-LS, etc. wavelet-base...
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Despite the approval of a new standard in 2009, JPEG-extended range lossless, current digital products still employ previous standards for lossless image compression, such as JPEG, JPEG2000, JPEG-LS, etc. wavelet-based codecs can provide abundant functionalities and excellent compression efficiency. Among them, the backward coding of wavelet trees (BCWT) algorithm offers lower complexity and consumes less internal buffer memory without sacrificing quality at similar compression ratios (CR) when compared to other wavelet- based codecs, such as JPEG2000 and set partitioning in hierarchical trees (SPIHT). A line-based BCWT was developed for further reduction of internal buffer memory. A very efficient line-based lossless BCWT compression algorithm is presented. Lossless color and lossless wavelettransform are employed and the original BCWT algorithm is modified for lossless operation, including incorporation of adaptive arithmetic coding. In order to eliminate coding redundancies, a set to zeros method and a zero tree detection algorithm are proposed, which significantly enhance the boundary condition CR performance while reserving the algorithm's advantages. Tests and analysis results show that the lossless BCWT algorithm requires less memory and computational resources than SPIHT and JPEG2000, while retaining image quality comparable to the standard image codecs, therefore, lossless BCWT is quite suitable for implementation in modern digital technologies. (C) 2014 SPIE and IS&T
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