Abstract: Considering the importance of image transmission in the public net， a new image encryption algorithm was proposed based on the 2DLogistic chaos and quadratic residue. Firstly， the original image was shuffled twice with the 2DLogistic chaos map， and the positions of the original image were changed sufficiently. Then， the shuffled image was turned into a binary sequence， and every 8 bits were called a block. For each block， quadratic residue was applied to encrypt the block， then， the encrypted binary sequence was turned into the encrypted image. Therefore， the statistical information of plain image was changed drastically by the proposed scheme. The proposed image scheme was tested by various types of experiment and security analyses such as histogram analysis， information entropy， key sensitivity and correlation coefficient analysis. All these analyses demonstrated that the proposed scheme can resist statistical attack， information entropy attack， and it is very proper for secure image communication.

Key words: image encryption, image permutation, image diffusion, 2DLogistic map, quadratic residue