Microsoft Office

Part IV
Using Advanced Excel Features
FIGURE 31.9
The Document Inspector dialog box identifies hidden and personal information in a workbook.
Using a digital signature
Excel lets you add a digital signature to a workbook. Using a digital signature is somewhat analogous to signing
a paper document. A digital signature helps to assure the authenticity of the workbook and also ensures
that the content hasn’t been modified since it was signed.
After you sign a workbook, the signature is valid until you make changes and resave the file.
Getting a digital ID
In order 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 authenticity.
Creating your own digital ID is useful if you want to ensure that no one has tampered with one of your
signed workbooks.
Signing a workbook
Excel 2007 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 information 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.
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