Invertible map set based image encryption algorithm

Utilizing the stretch and fold mechanism, an invertible map set based image encryption algorithm is proposed. The stretch process is to insert pixels of columns or rows of an image matrix into other columns or rows to map the image matrix to an array, while the fold process is to fold the array to an encryped image matrix according to a certain sequence. The size of the encryped image matrix the same as that of the original plain-image. Several stretch and fold maps are chosen to constitute an invertible map set. Each digit of a security key denotes a corresponding map in the map set. A sequence of map iterations are done according to the order determined by the key. The encryption and decryption algorithms are formulated. The simulation results show that this proposed encryption method has high diffusivity, high sensitivity to security key, large key space and high computing speed, and capability of image encryption and decryption in real time.