Archive for 28th February 2012

Android Phone as BitLocker Recovery Key

I recently ran into an issue where I needed my BitLocker recovery key, but found that I’d left it at home. This locked me out of my machine for a few hours and was a bit of a hassle. It got me wondering if maybe I should instead keep said key on my phone instead, as it does a pretty good job serving as a USB mass storage device.

It turns out that this is not such a keen idea, as it doesn’t work out very well. On my Nexus One (and presumably other Android phones), when connected to a computer they prompt the user to switch the microSD storage over to USB Mass Storage. Once selected this takes a few seconds. Whenever the phone is disconnected from the USB host it automatically presents the card back to the phone, and only prompts the user once a host is detected.

With BitLocker, one becomes aware of needing this key when the boot is interrupted and the user is prompted to insert a USB mass storage device with the key present. The computer is then rebooted, finds the key, and continues to boot. With an Android device as the USB mass storage device this reboot resets the phone. I’ve found that it’s typically not possible to get the phone into mass storage mode between POST and OS load, particularly as the machines I’ve tried it on seem to reset USB after POST.

I think I’ll just have to stick with a USB flash drive for this.