Abstract：Very recently, several chaos-based image ciphers using a bit-level permutation have been suggested and shown promising results. Due to the diffusion effect introduced in the permutation stage, the workload of the time-consuming diffusion stage is reduced, and hence the performance of the cryptosystem is improved. In this paper, a symmetric chaosbased image cipher with a 3D cat map-based spatial bit-level permutation strategy is proposed. Compared with those recently proposed bit-level permutation methods, the diffusion effect of the new method is superior as the bits are shuffled among different bitplanes rather than within the same bit-plane. Moreover, the diffusion key stream extracted from hyperchaotic system is related to both the secret key and the plain image, which enhances the security against known/chosen plaintext attack. Extensive security analysis has been performed on the proposed scheme, including the most important ones like key space analysis, key sensitivity analysis, plaintext sensitivity analysis and various statistical analyses, which has demonstrated the satisfactory security of the proposed scheme.

In this paper, we present an adaptive bilateral filtering algorithm that can be used to remove unavoidable noise from 3D mesh data generated by initial stages. Selecting the parameters for bilateral filters automatically, this algorithm smoothes meshes in the normal field using anisotropic character of local neighborhood triangles. Experimental results demonstrate that the proposed method remove light noise from meshes and reserve fine features of meshes as good as best results of other methods, with the advantage of none user-assisted parameters setting. Visual comparisons display that the method proposed in this paper performs better than other smoothing method for heavy noisy mesh.

Absuact-As multimedia data become more prominent in our daily life. the need for cfiicient image encryption will become mom important, especially in some emerging novel applications using image containing valuable information, such as ITS, hecause it is vulnerable lo illegal PCCUS during transmission over network. This paper introduces a new scheme, which combines Discrete Wavelet Transform (DWT), Embedded Zerotree Wavelet Algorithm ( E m ) , and Advanced Encryption Standard (DES). The object ofthis propmed scheme is to reduce the total amount of data by compression with DWT and EZW' first. and then, to enhance the security of stream by encryption with AES. T h m images of 512 X 512 pixels are used to verify the rharactcristier of this schemr Experiment results indicate that the proposed scheme protects the content of picture sent over network efkiently, and reduces the hit rate at the same time. This scheme can be applied for trafiic image transmission over network b d e r Tem-image compression, image encryption, DES, EZW'. AES

Abstract:It is well-known that for a given sequence, its optimal codeword length is fixed. Many coding schemes have been proposed to make the codeword length as close to the optimal value as possible. In this paper, a new block-based coding scheme operating on the subsequences of a source sequence is proposed. It is proved that the optimal codeword lengths of the subsequences are not larger than that of the given sequence. Experimental results using arithmetic coding will be presented.

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