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What is the LibreOffice digital signature feature and how do you use it?

If you want to ensure those who receive your documents can trust they come from you, the LibreOffice Digital Signature feature is a good place to start.
Written by Jack Wallen, Contributing Writer
sarayut Thaneerat/Getty Images

In this modern age of hacks, scams, and identity theft, it's always a good thing to help those you collaborate with to know that the document they've received is actually from you. Or maybe you simply need to send a document to someone and you want to be certain they can trust the document and the sender.

Also: How to install the latest version of the free LibreOffice office suite on Linux

That's why tools like LibreOffice include the ability to add a digital signature. Once you've added a digital signature to a document, a banner will appear, clearly indicating the document has been signed and even allowing the user to view the signature.

The LibreOffice Digital Signature banner.

My LibreOffice document has been successfully signed.

Jack Wallen/ZDNET

The only caveat to using this feature is that it can be tricky to set up. The primary reason for that is you need a certificate manager on your computer to make it work. For example, on Linux, you'll want OpenPGP and Seahorse installed. On MacOS you could use GPGTools and on Windows, you could use Gpg4win. I'm going to demonstrate on Linux, but the process of using digital signatures for LibreOffice is the same across platforms. The only variable is how you create your signing certificate.

With that said, let's make this work.

How to creating a signing certificate

What you'll need: The first thing you'll need is LibreOffice installed on your operating system. You'll also need a user with sudo privileges (for Linux). If you're working with either MacOS or Windows, you'll need to make sure you've installed one of the above certificate managers and used it to create a new certificate. I'll demonstrate this on Ubuntu Budgie (Linux). If you're using a distribution that is not based on Debian, you'll need to alter the installation command (for example, switching dnf for apt-get).

1. Install OpenPGP and Seahorse

If you've not already done so, you'll need to install both OpenPGP and Seahorse. To do that, open a terminal window and issue the command:

sudo apt-get install gpg seahorse -y

2. Create your GPG key

Next, you must create a GPG key with the command:

gpg --gen-key

You'll be asked for your name and email address, and then to type/verify a password. Once you've done that, you're ready to sign your documents. If you're using either MacOS or Windows, you should be able to generate your certificate from the GUI (instead of using the command line).

3. Open a LibreOffice document

Open LibreOffice and then open the document you want to sign. Do note, if you plan on creating a new document, you'll have to save it before you sign it.

Also: How to choose the right Linux desktop distribution for you

4. Open the Digital Signatures tool

Click the File menu in LibreOffice and then click Digital Signatures > Digital Signatures. In the resulting popup, click Sign Document.

The LibreOffice Digital Signatures window.

Make sure to click Sign Certificate and not Start Certificate Manager.

Jack Wallen/ZDNET

5. Select your certificate

In the next window, make sure to select the certificate you want to use (if you've generated multiples). It should then prompt you for the password you set for the certificate (when you first created it). Once you've successfully typed the password, you can close the Digital Signatures window, and rest assured your document has been digitally signed by you. Anyone who views the document can also view the certificate. 

A listing of certificates I've created for testing.

If you have multiple certificates, make sure to select the correct one.

Jack Wallen/ZDNET

 And that's all there is to adding a digital signature to your LibreOffice documents.

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