Input data is converted into an image, and in the input image, an encryption region that is a region in which the image is to be encrypted. Meanwhile, on the basis of an encryption key, encryption key-related information that is information related to the encryption key is generated, and the encryption key-related information is embedded into the image in the encryption region, to generate a first intermediate image. Next, the first intermediate image is converted on the basis of the encryption key, to generate a second intermediate image. Then, the pixel values of the second intermediate image are converted so that the position of the encryption region can be specified. As a result of the conversion, an encrypted image in which the part corresponding to the encryption region in the input image is generated.