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AutoCAD Tutorial

AutoCAD 2004: Digitally Sign Your Drawings

by Alireza Parsai, April 28, 2003

A digital signature identifies an individual or an organization by using a digital ID. Nobody can forge or copy a digital signature. When you sign a drawing file by a digital signature, you give the file a certain authority. Any one opening the file is guaranteed that it came from you. By digitally signing the drawing file your clients make sure that you approve the content.

AutoCAD 2004 is accompanied with a utility that enables you to digitally sign your drawing files. If you have not obtained a digital signature you can refer to valid vendors to purchase one. (For example you can refer to Verisign to know more about digital signature.)

The following tutorial shows you how to use digital signatures in AutoCAD 2004.

Note: The tutorial is applicable for those who have a digital signature and AutoCAD 2004 is also installed on their computers.

Tutorial

1. Download the following files:

► R16 - 2D House.dwg
► R16 - 3D House.dwg
► R16 - Chair.dwg

2. In Windows click Start > Programs > Autodesk > AutoCAD 2004 > Attach Digital Signatures.

3. The Attach Digital Signatures dialog box appears [Figure 1].


Figure 1 - Click on image to enlarge

4. Click Add Files.

5. Locate and add the files [Figure 2].


Figure 2

6. In "Get time stamp from" select a source for assigning a time to your signature [Figure 3].


Figure 3

7. Add any comments you want to the Comment box [Figure 4].


Figure 4

8. Click Sign Files. A dialog box confirms the result [Figure 5].


Figure 5

9. Click OK and then close the main dialog box.

10. Start AutoCAD 2004.

11. Open "R16 - 2D House.dwg". Since the digital signature utility assigns Read-only attribute to the drawings a warning message appears [Figure 6].


Figure 6 - Click on image to enlarge

12. Click No and then press Esc to cancel opening the file.

13. In Windows, start My Computer and locate the files [Figure 7].


Figure 7 - Click on image to enlarge

14. Select the files. Right-click on one of them.

15. Select Properties. The Properties dialog box appears [Figure 8].


Figure 8

16. Deselect the Read-only attribute. Click Ok.

17. In AutoCAD 2004, open one of the drawing files (e.g. "R16- 2D House.dwg").

18. A dialog box confirms the validity of the digital signature [Figure 9]


Figure 9

19. Click Close.

20. Try to save the file. A warning message appears [Figure 10]. If you save the file the digital signature will become invalid


Figure 10

21. Click "Yes" to save the file.

22. Click on the digital stamp on the status bar tray [Figure 11].


Figure 11

23. A dialog box shows that the digital signature is not valid anymore [Figure 12].


Figure 12 - Click on image to enlarge

24. Click Close.

25. There is no way to revalidate the digital signature. But you can sign it again. To sign the file again you can use the external utility (i.e. Attach Digital Signature) or invoke the SECURITYOPTIONS command. To invoke this command you should type its name completely or use the Options dialog box.

26. Right-click in command window. Select Options.

27. In Options dialog box click Open and Save tab [Figure 13].


Figure 13 - Click on image to enlarge

28. Click Security Options.

29. In the Security Options dialog box select Digital Signature tab [Figure 14].


Figure 14 - Click on image to enlarge

30. Select "Attach digital signature after saving drawing".

31. Get the time from a proper source and add comments.

32. Click OK.

33. In Options dialog box click OK. Now when you save the file a new signature will be added to your drawing file.

Related Commands and system variable:

► SIGVALIDATE (command)
► SECURITYOPTIONS (command)
► SIGWARN (system variable)


About the Author

Alireza Parsai is the founder of cadpanel.com. He is a mechanical engineer with more than 12 years experience with AutoCAD. Alireza is an Autodesk Authorized Author, the AutoCAD consultant for Al Khawarizmi Institute, a contributing editor for Augiworld magazine, a writer for CAD Digest, an instructor for AUGI Training Program, and an elected speaker for Autodesk University 2002. He has written 7 books in Farsi, 3 booklets in English, and more than 30 articles for different magazines and newsletters. You can reach him at alireza.parsai@cadpanel.com or visit his website www.cadpanel.com

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