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I have a few Excel documents we need to sign at my job. Also some PDF ones. I've looked everywhere and all sites shows an "easy" answer but all lead to the same: obtain a digital id from microsoft. On their site they say "if you don't want to buy a certificate from a CA..." Well, we have one in a P12 format but I can't find a way to use it in Excel. The so called "signature line" forces you to get a microsoft id.

We signed the PDF files with FoxIt, which allows you to select a P12 file for signing the document. Anything like that on Excel?

By the way, which CA offers certificates for code signing?

Edit: Maybe the P12 file has to be installed in the certificate store, but I don't know whether it has to be local or personal, and in which part of the store should it appear. Maybe that's the reason that Excell asks to obtaing a digital id since it can't locate a certificate

alvaroc
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Thanks to information posted by Greg Belding at resources.infosecinstitute.com. This is the only time I've looked at that site.

https://resources.infosecinstitute.com/topic/using-certificates-in-windows-10/

The digital certificate must be imported. There are two ways to import certificates. Using certlm which imports to the local machine didn't work for me, as far as being recognized by Excel.

Instead I typed "run" in the Cortana run and search area and clicked the Run app. In that app I typed "certmgr.msc" and clicked OK. The window that appears will have a title starting with "certmgr".

In the left list click on Personal and then Certificates. In an empty area of the list to the right, right click, then click "All tasks", then click "Import..." Browse to the folder where your .p12 file is stored, and in the lower right, make sure the kind of files being shown are "All Files (.) Click on the desired file and click "Open". [I used a pfx file, but expect this method to work for a p12 file.]

Since the file contains a secret key (at least, it should) you will have to enter the password you selected when you previously exported the certificate into a file. I suggest clicking all the boxes under "Import options". In the next screen accept the default of placing the certificate in your personal store. Choose the level of security you want (I picked medium) and finish importing the certificate.

You should then be able to use the certificate to sign an Excel file, in the same sense that you would sign a Word document, to indicate some level of agreement with the document. Code signing is a different subject.

Gerard Ashton
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