In an image processing system according to the present invention, a first device encrypts image data generated by reading an image in a document, stores a decryption key for decrypting the image data, and transmits the image data to a data storing device. A second device receives the image data from the data storing device, sends a request for the decryption key to the first device and receives the decryption key, decrypts the image data with the decryption key, and performs print processing on the image data. Thus, users can easily perform print processing without the need to remember authentication and printer information.