关键词: 图像加密, 置乱, 扩散函数, logistic映射

Abstract: Nowadays most image encryption methods are mainly confined to square image encryption.In order to overcome this limitation，it proposes a new encryption algorithm which can be applied to both square and rectangular image encryption.Apply the new map that formatted through the folding and stretching of the image to the location scrambling，and change the grey of each pixel in the image by using spread function that contains chaos map，so as to get an image encryption algorithm which combines position and gray scrambling.The results of simulation show that this algorithm can achieve good image encryption of any size，and it has a satisfactory encryption effect.What’s more this algorithm has a large key space，key sensitivity and it also has many other advantages such as withstand statistical and known expressly attack.

Key words: image encryption, scrambling, diffusion function, logistic map