On Tue, Dec 31, 2002 at 10:21:47PM +0100, Thomas Shaddack wrote:
>
> One of my ideas was to put a small piece of film or photographic paper,
> detect that it was exposed to light, but then the adversary can put in a
> new piece of the light-sensitive material and reseal the package. The same
> problem goes with the various kinds of seals.
Isn't the obvious way to handle this to include an undeveloped
(latent image) photograph of some obscure object, person, or place on
the film rather than just a blank film ? ? You could then develop it
and check for light damage and evidence of lack of authenticity. I
suspect there are tricks involving calibrated exposures of objects with
known optical power ratios (a kind of hidden grey scale strip) or even
holograms superimposed on normal looking photographs of scenes that
might be rather hard to easily duplicate by developing the latent image
and making either an optical or contact print of it on a similar medium.
>
> Comments, hints, keywords to look up?
--
Dave Emery N1PRE, [EMAIL PROTECTED] DIE Consulting, Weston, Mass.
PGP fingerprint = 2047/4D7B08D1 DE 6E E1 CC 1F 1D 96 E2 5D 27 BD B0 24 88 C3 18
