An image scanning system includes an image scanner and a terminal device connected with the image scanner. The terminal device accepts a password, stores an image encryption key, encrypts the image encryption key with the password, sends the encrypted image encryption key to the image scanner, receives image data encrypted from the image scanner, and decrypts the image data encrypted using one of the image encryption key and an image decryption key corresponding to the image encryption key. The image scanner receives the encrypted image encryption key from the terminal device, accepts a password, decrypts the encrypted image encryption key with the password, performs document scanning to create image data, encrypts the image data using the image encryption key decrypted, and sends the image data encrypted to the terminal device.