Image processing method, manipulation detection method, image processing device, manipulation detection device, image processing program, manipulation detection program, and image formation medium

An image processing method for detecting alteration of data formed on an image formation medium on which a main data image and a copy detection latent image are formed. The method comprises a first image creation step of creating an image in a state identical to a state of an image which is obtained by scanning the image formation medium on which the main data image and the copy detection latent image are formed, a one-way value operation step of effecting a one-way value operation on the image created at the first image creation step to calculate a one-way value, an image conversion step of converting the one-way value into an image representing the one-way value, a second image creation step of creating an image by superimposing the image representing the one-way value, the main data image and the copy detection latent image.