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Digital Signature – What Is It & How Does It Work?

An Insight Into Digital Signatures & the Way It Works

In today’s generation, where online threats are becoming prevalent, it has become mandatory that we must take active steps in protecting the information and data we pass online. There are various ways to do it, and one of them includes Digital Signatures. Yes, professionals who heavily rely on passing on information online daily – sending documents and emails need a way to validate that information, file, or data, and thankfully Digital Signature offers the same.

What’s a Digital Signature?

As the name implies, Digital Signature is one of the processes that give assurance that received message hasn’t been altered in its transition. Whenever you digitally sign any document using a digital signature, you also add encryption, which is one-way hashing (it’s a mathematical function to sign and validate that signed file) achieved with the help of public and private key pair.
In other words, Digital Signature is the subset of Electronic Signature that makes use of digital certificates, PKI authentication, and encryption for security provided by the certificates offered by trusted certificate authorities like Sectigo. It tells users that the document or message they’ve received hasn’t been tampered with in its transition. It has come from the legit source.

How Digital Signature Works?

Let’s look at it with an example, where Alice digitally signs a document or an email and sends it to Bob.
  • First, Alice decides and selects the file she wants to sign, or in her email application, she’ll click on the sign option.
  • Once the file is selected, Alice’s computer will calculate the hash value of the file content or the message that has to be sent to Bob.
  • Next, the hash value of the selected file or message gets encrypted using Alice’s Private Key for creating the Digital Signature.
  • After it’s signed using Private Key, that original file or an email message will be sent to Bob along with the Digital Signature.
  • When Bob receives that signed message – the document or an email message, the associated application will identify that the received file is signed, then Bob’s computer will take other steps:
    • Decrypt that Digital Signature, which was attached using Alice’s Public Key.
    • Calculate the hash of that message.
    • Compare computed hash value from the received message with the decrypted hash value of Alice’s message.
  • If any difference is found, it’ll consider that the received message is not original, and it has been tampered with.
understanding digital signature

How to Create a Digital Signature

Recommended as per industry standard and security-wise, the best choice is to go for a third-party trusted certificate that you can obtain through respected certificate authorities like Sectigo. Though there’s one more option of creating a self-signed certificate, if you create that, recipients of your documents will fail to verify whether the digital signature is authentic or not. Also, they’ll have to go through a manual process to trust your self-signed certificate.

On the other hand, if you want your documents to verify the authenticity of your digital certificate without anyone’s intervention automatically, then you’ve to purchase a digital certificate offered by globally known and reputed certificate authorities. Once you download and install your certificate – you will be ready to Sign and Encrypt documents or mails digitally.

Lastly, it’ll be a sensible decision to get a digital certificate from the certificate authority, if you’re an organization whose document must be seen as coming from a trustworthy source for assuring users that they’re safe.

Other Ways to Use Digital Signatures

Digital signatures are used in various ways, along with X.509 certificates. Commonly you’ll find it with:

  • SSL/TLS Certificate – When it comes to websites, public key, along with a digital signature offered by a certificate authority, is used for establishing a secured connection between the client and the webserver.
  • Document Signing Certificate – Often, it happens that it has to be proved that a document that you’re about to open forms a trusted source, and it hasn’t been tampered with. For instance, a legal matter where it has to be proved that the contract hasn’t been altered.
  • Code Signing Certificate – If you’re a software developer, then you might know the importance of a code signing certificate. It uses a digital signature to assure customers that software or any other executable file they’re downloading hasn’t been tampered with, and it’s signed using a trusted certificate.

Types of Digital Signatures

Depending upon the processing platform you’re using, it’ll allow you to create different types of the digital signature. For example,
  • Adobe supports – Certified Signature and Approval Signature.
  • Microsoft Word supports – Visible signature and Non-Visible Signature.
Let’s see each of them in detail.

Certified Signatures

If you use a certified signature for your PDF document, it gives a message that you’re serious about your document and content, and you also care about the user’s security who receives it. It tells users that it’s coming from the author of the document, and it hasn’t been tampered with.
digital signature certified signature
These signed and certified PDF documents are displayed uniquely with a blue ribbon at the top left corner of the document. It consists of certain information like the name of the document signer, an issuer of the certificate for indicating the authenticity, and author of the document.

Approval Signatures

Approval signatures are usually used for signing an organization document where you want to optimize the organization’s approval process. The procedure for this simple captures your approval along with other individuals and embeds them within your PDF document.

Lastly, Adobe also lets you include details like the image of your physical signature, location, data, and official seal with signature.

Visible Digital Signatures

As the name implies itself, the signature is visible on the document similar to any signature you do on a physical document. It doesn’t matter whether there are one or multiple users, as all are allowed to attach their signature onto a single document.

Invisible Digital Signatures

The document will not display the signature, but it’ll show a visual indication through the blue ribbon in the taskbar. However, it’s possible to use an invisible digital signature, and it’s even helpful when you don’t want to display it. Still, you want to offer assurance to the user that the document they’ve is genuine, and it’s not tampered with.


In today’s date, online threats are prevalent, which has shown how significant it’s to secure the information shared over the internet, whether it’s any particular data, document, or any other thing. And, nowadays, even users are also aware that security threats shouldn’t be taken lightly, or else it can lead to a massive loss that could even take decades to recover for some of the organization.

Many security products are available in the market, along with the most important digital signature offered along with CAs certificate, which is something that shouldn’t be overlooked. By attaching digital signature, you’ll be able to provide trust and assurance to users that have needed before downloading anything.

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