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Re: ACAD Protection

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Is it possible to enclose a coding that will produce a message on any
drawing(s) revised without authority, a bit like a hidden cookie that would
require serious hacking to find and delete?

Thor Tandy  P.Eng  MCSCE
Victoria BC
-----Original Message-----
From: Mark Middlebrook <markmid(--nospam--at)>
To: 'SEAOC List' <seaoc(--nospam--at)>
Date: Friday, January 08, 1999 11:31 AM
Subject: Re: ACAD Protection

The "turn a DWG file into a PLT file" method of drawing protection is useful
to know about, but it's device-dependent (i.e., the recipient needs to have
an output device that's capable of accepting the plot file) and may not
serve the client's needs.

A PLT file is a simplified vector representation of your AutoCAD drawing.
The PLT representation contains vectors and instructions for how to show
those vectors (line thickness, color, screening, and any other special
effects), and that's about it. Layer information is absent. Text is
converted to vectors. Drawing structure (blocks, xrefs, etc.) is gone.
Essentially it's a plotted representation of your drawing in electronic

If the recipient has an output device that understands your PLT file format
(often HP-GL/2, the most common HP plotter format), then he can send the
plot files to that device and get plotted drawings. If she has a piece of
software that reads HP-GL/2 files, she may be able to view the plotted
representation on the screen. With such software, she also might be able to
convert the PLT to a different format (e.g., DXF) and bring it back into
AutoCAD. But the result back in AutoCAD will be a pale shadow of your
original DWG file (because of the loss of layers, text strings, drawing
structure, etc.). That's why people often advocate sending PLT files as a
means of drawing protection.

However, the client who asks for AutoCAD drawings often is interested in
doing something more than just plotting. Sometimes that "something more" is
legitimate (e.g., electronic coordination, or full electronic submittal to
the client). On the other hand, the firm that generates the AutoCAD drawings
has a legitimate concern that the drawings not be misused (e.g., relied on
uncritically for shop drawings, designs or details stolen...).

In my view, the concerns of all parties involved are best addressed in the
contract for design services, not by ex post facto attempts to protect the
drawings. Your contract should state exactly what your deliverables are
(both hardcopy and electronic) what they're to be used for, and what they
*aren't* to be used for.

- Mark Middlebrook