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To compress and encrypt images synchronously,ajoint compression-encryption algorithm by using a hyper-chaos Chen system and a improved zero tree coding was proposed.Based on the improved zero-tree coding,a key stream produced by the hyper-chaotic Chen system was used to modify the context and the decision after bit-plane encoding,then they were fed into a MQ arithmetic coder to compress and produce the corresponding code streams.The code streams were feedbacked into the input end of hyper-chaos Chen system to produce a new secret key related to the plaintext and to realize the joint compression-encryption.Experimental results indicate that the Peak Signal to Noise(PSNR)of proposed algorithm is improved at least 1dB,and the key space is 256 bit.The encryption time percentages of total time are all less than 45% and the plaintext and secret have higher sensitivity.The proposed algorithm realizes the synchronization of image compression and encryption,and the image reconstruction quality is higher than that of embedded zero wavelet.It is characterized by the high resistance for linear attack and differential attack,a large key space and better safetyperformance.

In order to solve the problems laid on continuous signal sampling based on finite rate of innovationm,the feature of piecewise linear sequences is studied seriously,and a method called sequence resampling is proposed where the continuous signal variation parameters is extracted in discrete domain.The finite rate of innovation of sequence with finite length is defined,and a parameter extract method called test method is concluded which is suitable for the parameter extract of simple linear sequences,then this method is extended to the one of normal linear sequences.The innovation number does not need to be known in advance,and complex operations in continuous domain can be avoided;the signal′s innovation time and parameters can be extracted from the sampled sequence,and the signal sampling is realized.The proposed algorithm is simulated,and the results show that the proposed algorithm is valid.

On the basis of careful research on arithmetic coding and arithmetic encryption,a kind of image joint compression encryption algorithm based on improved zero-tree coding is proposed,where a key is used to modify the original context and the original decision produced in the process of image compression,and the image joint compression-encryption is realized in this way.In this work,the rule of the context modification and the decision modification algorithm is discussed and its security is analyzed.In order to meet different application requirements,different keys are used to encrypt separately the different wavelet resolution coefficients during bit-plane coding,so the resolution selective encryption is realized.Moreover,the Zero-tree coding was improved,and adaptive arithmetic coding is introduced to the improved Zero-tree coding,and then joint compression-encryption algorithm proposed is simulated.The simulation results show that the proposed image joint compression-encryption algorithm has the same compression efficiency compared with the original image compression algorithm;and the proposed algorithm has better security than the joint compression-encryption algorithm based on the interval splitting.

A fast algorithm for T2 encoder in JPEG2000 suitable for hardware implementation is presented in this paper, based on the elaborate analysis of a rate-distortion optimization algorithm. By reducing calculative complexity, the difficulty of hardware implementation for the T2 encoder is reduced, and the parallelizability of the JPEG2000 hardware system is enhanced. The experimental results show that the final code stream is in accordance with the standard format of JPEG2000 and reconstructed image quality decreases little. The system has been implemented on FPGA

A novel joint compression-encryption algorithm based on embedded zerotree wavelet (EZW) coding is proposed. Encryption process is performed before entropy coding. The principles of the context modification and the decision modification and described. Simulation results show that the proposed algorithm has a good effect on security, and has the same compression efficiency compared to the original image compression algorithm.