I know that by configuring crypttab I can automatically unlock LUKS drives by using keyfile stored on another drive in the machine which has been manually unlocked in advance. I have been wondering if a keyfile stored in a different machine/device can also be used, accessed e.g. over ssh.
Here is what I would like to achieve. A machine with an encrypted LUKS drive would at startup look at a particular IP address in the local network and if a device (android phone) is present, it would read a keyfile from the device and use it to unlock its drive, otherwise it would ask for password.
Are there any better approaches to this? I have found that there exists blueproximity which does something similar for lock-screen.