Re: Single device secret
MJB7 suggested, "...obtaining entropy for a small low-powered device like this is *hard*."
The design of the fob could include one of those little tiny SMD multi-sensor chips, 6-axis, as well as perhaps a microphone and light, etc. The fob device could wake up once in a while to gather entropy from being carried around, and random noises. The hashing into entropy bits would be critical, so better use a proven algorithm.
All this could be embedded into the tiniest fob. Duty cycle can be managed down to infinitesimal, so effectively zero power. Less than 1cc volume.
Seems *easy*. :-)
Biting the hand that feeds IT
