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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? <<

There's nothing built into AutoCAD that provides any sort of drawing protection, either locking or stamping. It might be possible to write an ARX or VBA application that provided the functionality you describe, but if so, I suspect that it would be a non-trivial job.

If you're worried about unauthorized editing, you can take measures such as:

- Make a note of the last updated time for each drawing (TDUPDATE system variable or TIME command).

- Print the directory information (including date and time) of the DWG files that you submitted.

- Make archive plots for later comparison (11"x17" reduced-size often works nicely for this purpose, and are handy for later review).

- Again, make sure that your contracts cover what's allowed and what's not allowed.

Obviously none of these measures *prevents* anyone from editing your drawings, but they do give you documentation that can help you prove tampering and demonstrate exactly what you sent.

A company called CADLock ( makes a third party application for locking AutoCAD drawings. But again, I question whether this kind of approach is the right one for most situations that structural engineering firms encounter. Like all proprietary copy protection schemes, it increases the hassle factor (for oneself *and* one's clients). Moreover, the need to lock drawings often is a sign that the engineer-client relationship isn't a good one, or that contracts and communications haven't been attended to adequately.

Nonetheless, there's no reason that Autodesk couldn't add some sort of simple password protection to AutoCAD, a la the Microsoft Office applications. This feature is on the wishlist, but for whatever reason hasn't made it into the software. You could go to the Autodesk User Group International wishlist page ( and add your vote.

Way back in 1991 I wrote an article for CADALYST magazine on the copyright, liability, and other legal concerns in electronic drawing exchange. If there's interest, I can post it to the list (it's about 200 lines / 2000 words).

- Mark Middlebrook