Before taking the ends apart you need to connect the entire set to the PC, so that they can syncronize. This means that all the security information (PEK, KEK, Certificates,...) are identical on both ends. Once the process is done, you can take them apart and they will work together - no matter where you are.
When connecting the iTwin to the PC, regardless if both ends are attached to each other, you will get an Autorun screen. The software is embedded on the device and installed with the help of a virtual optical drive which is mounted as soon as you plug the device in. It also checks the Internet for the newest version of the application and updates itself automatically.
The next step is a security measure if you ever loose one end of the iTwin. By entering your email address, you can deactivate both ends of the device. For such a service you need to give your email address to the manufacturer to enable this ability. If you are a business user and have sensitive files within the iTwin ecosystem I strongly suggest taking advantage of this service - especially since it is free.
Once the app is up and running, you get two different context menus, depending if only one end is plugged in, or if you have both ends connected to each other. If both are present, like in the setup picture above, you are able to set a password and the emergency email address. Once they are apart the software only allows you to switch between the local and remote folders.
I am really surprised how dead simple the iTwin works. You basically drag and drop the files you would like to have accessible into the local folder of the application, which then appear on the second system as remote files. That same process can be done the other way around. You may also place file into the other end's folders by simply dragging and dropping them into the window. This is so easy anyone can use it. Another upside of such a simple, automatic implementation is the fact that it does not allow for many places of attack. The core function - the secure transfer of data between two endpoints seems to work extremely well. This is like using a online folder without the limit and without the need for an extra application or personal account.
Setting the password itself is very easy as well and the application keeps things simple with straightforward error messages, like when it cannot find the other end of the iTwin or if there is no Internet connection available.
Looks like the iTwin updates itself upon connection with the Internet, as there is a little check-box in the "About" dialog box.