For Liars and Loafers, Cellphones Offer an Alibi

[Thomas Shaddack]

On Sat, 26 Jun 2004, Major Variola (ret) wrote:

> I'm fully aware the pigs track you unless the battery is removed or you
> have a TEMPEST case.  I'm suggesting that regular citizens will have
> access to that, if (in my cluelessness) they don't already.

If the phone is shielded, it can't transmit/receive, which makes it rather
useless. :(

There is one potential landmine as well; the inherent ability of any
device containing resonators to behave like a crude RFID tag. I heard
somewhere, and my memory may be failing, that it is possible to irradiate
the phone with the frequency of the cellular band, and it faintly
resonates and returns back its own echo, which has minute variations given
by type, manufacturing tolerances, and possibly age of the phone, giving
it a kind of unique signature. (This could potentially apply also to
radios and transceivers. Does anybody have any idea if it is possible to
do such kind of "active fingerprinting" of rf devices? This way it should
be possible to detect even powered-off devices like hidden transceivers or
body wires; take a transmitter, sweep the spectrum, and watch echoes on
the receiver - there could be peaks on the frequencies of the tuned
circuits inside the examined device.)

Question to RF heads here: could it work?