Identity is tricky. Proving who you are depends on a certain level of trust. Whether it's through email, devices, phones, or, in more advanced settings, some sort of digital certificate; you won't have much options.
Unless you're in Germany using a service provided by the Vogons, you might end up getting a letter containing an activation PIN via snail mail or worst having to visit the post office to show your passport.
Unless you're in Germany using a service provided by the Vogons, you might end up getting a letter containing an activation PIN via snail mail or worst having to visit the post office to show your passport.