884 Part V Organizing and Managing Drawings

14.Click OK twice to return to your drawing. Pick an insertion point for the table.

15.Save and close any open drawings.

Maintaining Security

In these days of collaboration and interconnectivity, maintaining security is an important issue. Two features help you to keep your designs secure: password protection and digital signatures.

Password protection

Password protection ensures that unauthorized people don’t open your drawings. You create a password when you save a drawing.

AutoCAD LT does not offer password protection.

To create a password for a drawing, type securityoptions on the command line. If you’re saving a drawing for the first time, you can also click the Tools drop-down list and choose Security Options. The Security Options dialog box opens.

To password-protect a drawing:

1.Type a password in the text box.

2.If you also want to encrypt drawing properties that identify the drawing, such as the title, author, subject, and keywords, check the Encrypt Drawing Properties check box.

3.Click OK.

4.The Confirm Password dialog box appears. Retype the password.

5.Click OK.

You can also change or remove a password:

1.Open the Security Options dialog box.

2.Type a new password or delete the current password. Click OK.

3.If you type a new password, reconfirm the password and click OK.

The dialog box displays the current encryption type. To specify a different encryption, click Advanced Options. Choose a new encryption type from the list and a key length, and then click OK.

When a password-protected drawing is opened, the Password dialog box appears. To open the drawing, type the password and click OK.

Digital signatures

A digital signature uses software that confirms who signed the drawing and that it has not been changed, as well as non-repudiation (so that signers cannot claim that they never signed the drawing). To use a digital signature, you need to purchase a digital ID. You can use digital IDs in both AutoCAD and AutoCAD LT.

Generally, you would use a digital signature when you send a drawing to someone else. That person can then verify that the drawing is from you and has not been changed. If the person sends the drawing back to you, you can verify that the person has not changed the drawing, because changing the drawing invalidates the digital signature.

Note The Digital Signatures tab of the Security Options dialog box contains a link to VeriSign, a company that sells digital certificates. You can obtain a 60-day free trial or purchase a digital ID at one of several levels of security. If you don’t have a digital signature and want to use VeriSign, choose Tools Options and click the Open and Save tab. Click Security Options and then the Digital Signatures tab. A message displays, explaining that you don’t have a valid digital ID. Click Get a Digital ID to go to VeriSign’s Web site. Follow the instructions at the site to sign up for and install the digital ID. Although the initial Web page is specific to Autodesk, the final instructions assume that you want to use the digital ID for e-mail. You can ignore those instructions.

To attach a digital signature to a drawing, follow these steps:

1.Choose Tools Options and click the Open and Save tab. Click Security Options and then the Digital Signatures tab.

2.Choose a digital signature and check the Attach Digital Signature after Saving Drawing check box.

3.To place a time stamp on the drawing, choose one of the options from the Get Time Stamp From drop-down list.

4.To add a comment (that appears when the drawing is opened), type the text in the Comment text box.

5.Click OK.

When a digitally signed drawing is opened, the Digital Signature Contents dialog box appears, verifying the digital signature and the fact that the drawing has not been changed since it was signed. Click Close to close the dialog box.

Note that making any changes to the drawing invalidates the digital ID. If you make changes or try to save a drawing with an attached digital signature, a message appears asking you whether you want to continue. When you re-open the drawing, the Digital Signature Contents dialog box appears, displaying the fact that the digital signature is invalid.

A drawing with a valid digital signature has a checkmark attached to its icon in Windows Explorer. The drawing itself also sports an icon in the status bar, as shown in Figure 26-27.

Figure 26-27: A drawing with a valid digital signature, shown in Windows

Explorer and on its status bar.

886 Part V Organizing and Managing Drawings

Keeping Track of Referenced Files

A drawing references several types of outside files, and you often need to keep track of these files, especially when you send a drawing to someone else or move it to another computer. Also, the referenced files may be moved, even if the drawing stays in the same place. Without these outside files, the drawing is not complete.

AutoCAD LT does not include the Reference Manager.

Outside files include:

Other drawings (xrefs)

Text fonts

Images

Plot configurations

The Reference Manager not only lists referenced files, but also enables you to change saved reference paths so that the drawing can find the needed files. You don’t even need to open the AutoCAD drawing, because the Reference Manager is a stand-alone application.

To open the Reference Manager, choose Start [All] Programs Autodesk AutoCAD 2006 Reference Manager. The Reference Manager is shown in Figure 26-28.

Figure 26-28: The Reference Manager.

To add drawings to the Reference Manager, click Add Drawings and select the drawings. If a drawing has xrefs, you see a message asking whether you want to add the xrefs. To add them, click Yes.

The left pane of the Reference Manager contains a tree view of the drawings that you’ve added and external references, if any. The right pane is a Reference list and displays the

Handling Errors and Crashes

Although AutoCAD 2006 and AutoCAD LT 2006 are stable, and the latest versions of Windows are more stable than previous versions, nothing can eliminate the occasional crash. Knowing how to reopen a drawing after a crash can save hours of work.

Taking care of temporary files

When AutoCAD or AutoCAD LT is loaded, it opens one or more temporary files as part of its normal functioning. Note the following two points regarding these files:

You need to leave room on your hard drive for these files — 50MB is a good starting point.

Never erase current temporary files if you’re on a network, because someone else might be using them.

888 Part V Organizing and Managing Drawings

However, if the program or your entire computer crashes, you’ll probably be left with one or more .ac$ files. A good guideline for erasing .ac$ files is to only erase those from yesterday or earlier. Leave today’s alone.

You can also specify where you want these temporary files. You might want to place them on a hard drive with more room. If you’re on a network, you might want to place them on your local drive so that there is less traffic back and forth on the network. To find or change the current location, follow these steps:

1.Choose Tools Options. Click the Files tab.

2.Click the plus sign next to Temporary Drawing File Location to display the current location.

3.If you want to change the location, click Browse.

4.In the Browse for Folder list, find and choose the desired folder and click OK.

5.Click OK to close the Options dialog box.

Repairing corrupted drawing files

The most common cause for a corrupted drawing file is a program crash, but power surges and system crashes can also be causes. If AutoCAD or AutoCAD LT detects an error in a file during loading, it attempts to fix the problem automatically. In many cases, it is successful.

When it isn’t, you can try the AUDIT or RECOVER commands. These commands search the database for errors and try to fix them. If they cannot fix an error, they simply move on, letting you recover at least part of the file.

If you have a drawing open and see an error message that AutoCAD or AutoCAD LT can’t read the file or part of it, follow these steps:

1.Choose File Drawing Utilities Audit.

2.At the Fix any errors detected? [Yes/No] <N>: prompt, type y to fix any errors.

3.Watch the screen as it displays messages for errors.

Use RECOVER when you can’t even load the drawing. Follow these steps:

1.Open a new drawing.

2.Choose File Recover.

3.In the Select File dialog box, choose the corrupted drawing file and click Open. The recovery process starts and displays the results in the Text Window.

The DWGCHECK system variable controls how your drawings open when they have errors. Look up this system variable in Help to find a setting that gives you the information and control that you need. Here are some other tips for opening a recalcitrant drawing:

Open a new drawing and choose Insert Block. Click Browse and insert the problem drawing as a block. (See Chapter 18 for more information on blocks.) Then use the AUDIT command.

Open a new drawing and choose Insert External Reference. Locate and attach the problem drawing as an external reference. (See Chapter 19 for more information on external references.) Then use the AUDIT command.

If the drawing crashes just when it looks like it has almost loaded, try again; however, this time, press Esc repeatedly until the loading is complete. This procedure aborts the regeneration of the drawing, which may be causing the crash due to corrupt objects. Then use the AUDIT command.

If you can open the drawing but objects are not displayed, try the following:

•Choose File Save As and save it as a new drawing.

•Use the WBLOCK command to save the drawing as a new file.

•Save the drawing as a DXF file. (See Chapter 27 for more on the DXF file format.)

•Use File Save As or save as a DXF format, but to an earlier version of AutoCAD or AutoCAD LT.

Thanks to Darren Young of Minnesota CADWorks, Inc. (www.mcwi.com) for these suggestions.

Yes, AutoCAD does occasionally crash. A new feature in AutoCAD 2006 and AutoCAD LT 2006 makes recovering from a crash easier by displaying available backup drawings for you. If you crash, you first see the message shown in Figure 26-29.