The current process of adding devices to a share is kept simple and fast. Copy the key, paste, the device has access to the share. The major drawback here is that the key, should it fall into wrong hands, immediately allows an attacker full access to the share. For example when the mobile phone QR code is presented on screen, a camera across the room could easily catch that. I propose a list of known devices shared within the folder. When a new device appears, a dialogue would appear on all currently active devices asking for permission to add the new device. A "yes" would add the device to