The Multiple And Signal Encryption Algorithm Research Based On JPEG-LS

With the rapid development of multimedia communication and computer technology, image acquisition equipment can collect more high resolution images. However, the clearer image contains the greater amount of information, and the requirement of storage space and network bandwidth is also higher. On one hand, people expect that the image can be transmitted rapidly and at the same time to obtain high-quality reconstructed image so as to continue studying or collection; On the other hand, people want to ensure that the image information cannot be stolen throughout the transfer process to implement safe and reliable transmission. Therefore, the compression and encryption for the lossless image is particularly important.At present, the jointly compression and encryption for the images are mainly concentrated on lossy compression and encryption. To some extent, this way can solve the security problem of image transmission, but there will be some loss of the quality of the reconstructed image, which does not meet people’s needs. JPEG-LS is a widely used compression standard for lossless or near lossless continuous-tone static images, which has the characteristics of low complexity, high compression ratio, and high flexibility. If the JPEG-LS lossless compression and image encryption are combined, it will meet people’s demands.In this paper, based on the study of JPEG-LS, it researched the single and multiple encryption for the key parameters of the JPEG-LS encoder so as to complete fast coding and decoding as well as realize lossless compression and encryption of images simultaneously. The main contents of this paper are summarized as follows:(1)The generation of the key:A way to produce the key stream which combined the chaotic system and optical Fresnel diffraction system was designed. It used Logistic chaotic map to simulate the original optical field distribution, and then the sequence was subjected to Fresnel diffraction multiple transforms, finally the key stream needed by the encryption was acquired.(2)The research of single and multiple encryption:For the normal mode, according to the characteristic of JPEG-LS itself which simultaneously decodes and outputs, if the coding order k and the parameter Q are corrected, we can ensure the image information would not be stolen, and at the same time the shortcomings that encryption method must be reversible in traditional way can be avoid, which is able to be proved in the theory, and it greatly expands the correction space. Considering the balance of the encryption quality and compression performance, in this paper, the method of threshold interception was used to correct the important parameter k of Golomb coding, and the method of the left shift modulus operation was employed to revise the parameter Q. And the experiments has proved that the feasibility and security of the encryption algorithm were high. Besides, for the run mode, an encryption algorithm using random key stream of "0" or "1" to encrypt the coden word separators was designed, with strong ability to resist ciphertext attack and the ability of statistical analysis. For the multiple encryption mode, it mainly analyzed the impact of three encryption mode for the compression performance of JPEG-LS encoder, and its effectiveness was explained by experimental data. The three modes are k and Q are simultaneously encrypted, k and run mode are simultaneously encrypted, Qand run mode are simultaneously encrypted.