Security Analysis of JPEG Image Encryption Algorithm Based on DCT Coefficients Shuffling and Decomposing

In this paper, security of a JPEG image encryption algorithm has been analyzed. The algorithm shuffles DCT quantization coefficients in defined block and decomposes DC coefficient to change the number of nonzero DCT quantization coefficients in each 8 ^* 8 block. Chosen plain-text attack could be employed to recover the defined block shuffle. Changing the number of nonzero DCT quantization coefficients in each block still leaks plain-text image information. Numbers of nonzero coefficients counting attack is adopted to get mosaic appearance image of the original plain-text.