This article explains digital signatures (also known as digital ID), what they can be used for, and how you can use digital signatures in the following Microsoft Office programs: Word, Excel, and PowerPoint.
What is a digital signature?
A digital signature is an electronic, encrypted, stamp of authentication on digital information such as e-mail messages, macros, or electronic documents. A signature confirms that the information originated from the signer and has not been altered.
Signing certificate and certificate authority
Signing certificate To create a digital signature, you have to have a signing certificate, which proves identity. When you send a digitally-signed macro or document, you also send your certificate and public key. Certificates are issued by a certification authority, and like a driver’s license, can be revoked. A certificate is usually valid for a year, after which, the signer must renew, or get a new, a signing certificate to establish identity.
Certificate authority (CA) A certificate authority is an entity similar to a notary public. It issues digital certificates, signs certificates to verify their validity and tracks which certificates have been revoked or have expired.
What does a digital signature guarantee?
Non-repudiation Proves to all parties the origin of the signed content. Repudiation refers to the act of a signer denying any association with the signed content.
Notarization Signatures in Word, Excel, or PowerPoint files, which are time stamped by a secure time-stamp server, under certain circumstances, have the validity of a notarization.
To make these assurances, the content creator must digitally sign the content by using a signature that satisfies the following criteria:
Important: Signed documents, which have a valid time stamp, are considered to have valid signatures, regardless of the age, or revocation status, of the signing certificate.
Signature lines in Word and Excel
A signature line resembles a typical signature placeholder that might appear in a printed document. However, it works differently. When a signature line is inserted into an Office file, the author can specify information about the intended signer, and instructions for the signer. When an electronic copy of the file is sent to the intended signer, this person sees the signature line and a notification that their signature is requested. The signer can:
When the signer adds a visible representation of a signature to the document, a digital signature is added at the same time to authenticate the signer’s identity.
Create a signature line in Word or Excel
On the Insert tab, in the Text group, click the Signature Line list, and then click Microsoft Office Signature Line.
Instructions to the signer Add instructions for the signer, such as “Before signing the document, verify that the content is correct.”
Allow the signer to add comments in the Sign dialog box Allow the signer to type a purpose for signing.
Sign the signature line in Word or Excel
To select an image of your written signature, click Select Image. In the Select Signature Image dialog box, find the location of your signature image file, select the file that you want, and then click Select.
In addition, you can sign a signature line by double-clicking the signature line. Type your name next to the X. Or, in the Signature Pane, in the Requested Signatures section, click the arrow next to the signature. From the menu, select Sign.
To add a handwritten signature (Tablet PC users only), sign your name in the box next to the X by using the inking feature.
Remove digital signatures from Word or Excel
Note: In addition, you can remove a signature by clicking the arrow next to the signature in the Signature Pane. Click Remove Signature.
Invisible digital signatures in Word, Excel, or PowerPoint
An invisible digital signature, such as a visible digital signature line, assures the authenticity, integrity, and origin of a document. You can add invisible digital signatures to Word documents, Excel workbooks payday loans Massachusetts, and PowerPoint presentations.
Signed documents will have the Signatures button at the bottom of the document. In addition, for signed documents, signature information appears in the Info section that you see after you click the File tab.
Add invisible digital signatures in Word, Excel, or PowerPoint
To protect the authenticity of a document’s content, you can add an invisible digital signature. Signed documents have the Signatures button at the bottom of the document.