Didier Stevens

Monday 5 January 2009

Howto: Add a Digital Signature to an Office Document

Filed under: Encryption — Didier Stevens @ 21:19

Starting with Microsoft Office 2003, digital signatures can be added to office documents (e.g. a spreadsheet). Macros can also be digitally signed. So if you’ve that special spreadsheet macro to execute, but your Excel configuration requires macros to be signed, this howto is what you’re looking for 😉 .

First step is to import our PKCS12 file.

First we’ll take a look ad signing the document (an Excel spreadsheet).

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Adding a digital sigature is done with Tools / Options…

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These actions added our digital signature:

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Of course, when we change the spreadsheet, we have to sign it again:

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The title bar warns us when we opened a signed spreadsheet:

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The “unverified” word in the title is a reminder that we have to check the signature (via Tools / Options…) to make sure the spreadsheet wasn’t tampered with:

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Now let’s sign a macro:

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A default Office 2003 install requires macros to be signed:

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