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Re: Fingerprinting Paper with Laser
From: T Biehn <tbiehn () gmail com>
Date: Fri, 19 Mar 2010 23:13:46 -0400

What 'limits'? What 'acceptable range' are you talking about?
I think they scan the surface doing pit depth / pit counts like an expensive
cd reader.
Within this presumption, you have to fingerprint either the whole document
or a small square. It cannot be duplicated, it cannot be used to
authenticate 'batches.' It could only be included in some piggyback data
e.g. in the smartcard. Preferrably signed. With some glorious pki.

Keep trying,


On Mar 19, 2010 7:20 PM, "mrx" <mrx () propergander org uk> wrote:

Hash: SHA1

Valdis.Kletnieks () vt edu wrote:

On Fri, 19 Mar 2010 20:51:40 -0000, mrx said:
Consider a production line for printing anything ...
If deviations in the manufacturing process were consistently between known
limits, it still serves as a control.
A hacker may learn those limits but then the problem of recreating an equal
manufacturing process still remains.
Obviously if the deviation in each sample is such that the known level of
consistency is so wide that the process is easily
replicated then the tech is useless as an indicator of integrity.

A bigger concern is whether normal wear and tear will invalidate the
measurements - some spots ...
Yes I would agree, but for tokens of limited lifetime perhaps there is still
Concert tickets, travel tickets etc.
Besides one could always force renewal of the token once it's valid lifetime
has expired.

I still think there may be a potential security benefit here.


- --
Mankind's systems are white sticks tapping walls.
Thanks Roy


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