Add or remove a digital signature in Office files

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Add or remove a digital signature in Office files

This article discusses digital signatures (also known as digital IDs), their scope, and their use in the following Microsoft Office programs: Word, Excel, and PowerPoint.

Content of this article

What is a digital signature?

Signature lines in Word and Excel

Create a signature line in Word or Excel

Sign the signature line in Word or Excel

Delete digital signature  from Word or Excel

Invisible digital signatures in Word, Excel or PowerPoint

Add invisible digital signatures in Word, Excel, or PowerPoint

Remove invisible digital signatures from Word, Excel, or PowerPoint

What is a digital signature?

A digital signature is an electronic authentication buffer encrypted on digital information such as emails, macros or electronic documents. The signature confirms that the information originates from the signatory and has not been modified.

Certificate of Signature and Certificate Authority

Signing certificate      to create a digital signature, you must have a signing certificate that reveals the identity. When you send a macro or a digitally signed document, you also send your certificate and public key. Certificates issued by a certification authority and the license of a driver may be revoked. A certificate is usually valid for one year, after which the signatory must proceed with the renewal or obtain a new signature certificate to establish the identity.

Note:  You can learn more about private and public keys in this article.

Certification Authority      A certification authority is a similar entity to a notary office. It issues digital certificates, signs them to verify their validity, and tracks certificates that have been revoked or expired.

Tip:  For more information on obtaining a digital certificate, see Obtain Digital Certificate and Create Digital Signature.

What does a digital signature guarantee?

Authenticity      The signatory is confirmed as such.

Integrity      The content of a document has not been modified or falsified since it was digitally signed.

Non-repudiation      Provides all parties with the origin of the signed content. The term repudiation refers to the act of a signatory rejecting any link with the signed content.

Electronic notarization      in some cases, the signatures inserted in Word, Excel or PowerPoint files and time stamped by a secure time stamping server have the value of electronic notarization.

To provide these warranties, the creator of the content must digitally sign it with a signature that meets the following criteria:

The digital signature is valid.

The certificate associated with the digital signature is effective (not expired).

The signatory person or company, also known as the “publisher”, is approved.

Important:  Signed documents, whose timestamps are valid, are considered to have valid signatures, regardless of the age or revocation status of the signing certificate.

The certificate associated with the digital signature is issued to the signatory publisher by a recognized certification authority.

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