[Printers] obfuscate dots?

[Greg Johnson]

I have been servicing Minolta, Toshiba, Ricoh, Lexmark and HP 
printers/copiers for eleven years.  I am unaware of a way to defeat the 
anti-counterfit technology from a hardware or RIP standpoint.

As for edge offset, the printers have hard margins built in that will not 
allow normal printing all the way to the edge of the paper.  I would imagine 
that the dot pattern would repeat over the entire page with no margins.

You are correct in that the dot pattern is introduced to the image in the 
engine and written to the photoconductor through the normal printing process 
but there IS additional hardware involved.  Every color copier I have ever 
worked on has an "X-board".  This is a circuit board that you will not find 
in the schematic diagram and tech support will not even confirm it's 
exsistance when speaking to factory certified technicians.  We assume that 
this is where the magic happens, there has even been some talk that this 
component is supplied (or at least spec'ed) by the Treasury Dept.

In addition to the "X-board", some devices have a system that "validates" 
the imaging circuits.  For example, The serial number and other device info 
is hard coded into several different circuit boards in the machine and these 
components do a sort of handshake when the machine is powered up.  If more 
than one of these parts does not have matching information the machine 
assumes that someone is trying to bypass the anti-counterfit system and the 
machine locks down.  Requiring the manufacturer to send a rep. who gathers 
and submits some machine specific info to get an "unlock code".

We do not know who the info is being submitted to or exactly what is being 
reported, the factory reps who do this are very quiet about it and I am told 
there are only a handfull of authorized reps in the country.

I am always trying to learn more about the machines that I work with, so If 
I can be of assistance (technical or otherwise) in the hunt for information 
about this process, please let me know.

Greg


>From: Seth David Schoen <schoen at eff.org>
>To: Ringo Kamens <2600denver at gmail.com>
>CC: printers at frotz.zork.net
>Subject: Re: [Printers] obfuscate dots?
>Date: Sun, 15 Apr 2007 17:55:48 -0700
>
>Ringo Kamens writes:
>
> > Unfortunately it wouldn't work. To the naked eye it would work but I
> > think that forensics would be able to tell that they were made
> > differently. Wouldn't it just be better to completely remove/cover the
> > device that puts the yellow dots in? I also had similar questions and
> > would appreciate a response from somebody more in the know.
>
>My current opinion is that the dots are produced by the same mechanism
>as regular printer output; that is, they are added by software inside
>the printer rather than produced by separate imaging hardware.
>
>If they are pixel-sized and pixel-aligned, and always appear in the
>same offset to the edges of the paper, it should be possible to produce
>some kind of obfuscating overlay.  I know that I've argued in the
>past that this was impossible, but I now think it would be possible
>if the printer dots produced by a particular printer model are really
>made of ordinary yellow pixels and if their offset to the edges of the
>page isn't randomized.
>
>Actually getting this right is a little bit tricky, but I've recently
>experimented with printing 1x1, 2x2, and 3x3 pure yellow squares at
>fixed locations on an HP Color LaserJET and then looking at them under
>a microscope to compare with the tracking dots the CLJ is adding.  The
>results are promising but not at all definitive; one thing that would
>help is a much better microscope to try to clear up the question of
>whether the tracking dots are distinguishable under much greater
>magnification.)
>
>I'll try to give an update about this soon; I'm going to be speaking
>about printer dots at the meeting of the National Association of Document
>Examiners next month and I'm hoping to be able to tell them more about
>whether this countermeasure would actually work.
>
>--
>Seth Schoen
>Staff Technologist                                schoen at eff.org
>Electronic Frontier Foundation                    http://www.eff.org/
>454 Shotwell Street, San Francisco, CA  94110     1 415 436 9333 x107
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