Chapter 31: Protecting Your Work
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FIGURE 31.9The Document Inspector dialog box identifies hidden and personal information in a workbook.
After you sign a workbook, the signature is valid until you make changes and resave the file.Getting a digital ID
To digitally sign a workbook, you must obtain a certificate from a certified authority who is able
to verify the authenticity of your signature. Prices vary, depending on the certificate granting
company.Another option is to create your own digital ID, but others will not be able to verify the authentic-
ity. Creating your own digital ID is useful if you want to ensure that no one tampers with one of
your signed workbooks.Signing a workbook
Excel supports two types of digital signatures: a visible signature and an invisible signature.To add a visible digital signature, choose Insert ➪ Text ➪ Signature Line ➪ Microsoft Office
Signature Line. Excel displays its Signature Setup dialog box, and you’re prompted for the informa-
tion for the signature. After you add the signature box, double-click it to display the Sign dialog
box, where you actually sign the document either by typing your name or uploading a scanned
image of your signature.Figure 31.10 shows a document with a visible digital signature.