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Re: photocopy security management
From: "Gregory Rubin" <grrubin () gmail com>
Date: Fri, 3 Mar 2006 13:12:10 -0800

If I read this correctly, there are two different questions that you
could be asking:
1) How do I prevent people from copying sensitive documents?
2) How do I know who copied a sensitive document?

The first question is not one that I have the knowledge to answer. 
The second question relies upon "fingerprints".  A fingerprint is a
type of watermark that identifies the "user" or "owner" as opposed to
the source.  An example would be that one of my watermarked documents
might say "NationStates.net" but a fingerprinted document would say
"Greg Rubin".  I'm working on pulling up references on fingerprinting
(I think that they are at home), but there are essentially three ways
of doing this.

1)  Vary the font.  If you pick two very similar fonts and "randomly"
scatter letters of one font through the document of the other, you can
look at the photocopies to determine which characters are in the
secondary font and use that to identify the person who leaked the
2) Vary the language.  Use synonyms in various places throughout the
document, maybe a misspelling or two, or reword a sentence to be
semantically identical.  Make the changes different for each receiver
of the document.  You can then use these differences to identify who
leaked the document.  I should note that while I'm not a lawyer, I've
been informed that there can sometimes be legal issues with this one
because you have non-identical copies of the same document, so which
one is "official"?
3) Vary the layout.  The best versions of this minutely vary the
line-spacing and the word centroids.  This is so small as to be
imperceptible to the human eye, but can be detected and read by a
scanner and software.

Each has different strengths and trade offs.  I'll try to find some
journal references for you later today.

Greg R.

-----Original Message-----
From: Fco. Borja González [mailto:borjagonzalez () gmail com]
Sent: Thursday, March 02, 2006 7:24 PM
To: security-basics () securityfocus com
Subject: photocopy security management

Hi all,

Does anyone know anything about photocopy security management solutions?

The target is to avoid confidential documents to be copied. Things
like watermark the confidential documents while printing or techniques
like that.


Fco. Borja González
borja.gonzalez () gmail com

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