Systems and methods are provided for authenticating image files when network connections should not or cannot be used to transfer image files. A user device application may capture an image at a user device, generate an image file, and generate a hash file based on the image file. Instead of sending the image file to an authentication server for authentication, the application may send the hash file. If desired, the application may transfer the image file when a desirable network connection is available. Any alteration to the image file in the meantime will result in a different hash file for the altered image file, thus allowing detection of altered image files. This approach offers decreases the amount of data that is required to be transmitted in low or undesirable signal conditions, while maintaining an ability to detect alterations to image files that may have been made in the meantime.