What is a Digital Signature and How Does it Work?

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Wondering how digital signatures can help you? Here’s the answer

Every day, we send and receive loads of data on the internet. This includes text, pictures, documents, and many other forms of data. Since a lot of this information is sensitive in its nature, it’s essential to protect its validity and authenticity. In other words, it’s vital to know who created the message and to ensure that it hasn’t been altered since its creation.

One of the most popular and effective ways of validating the authenticity of a digital message or document is by using a digital signature. But what is a digital signature and how does it work?

So, What is a Digital Signature?

Digital signature is a technology that verifies the authenticity of digital messages or documents. A message or document that’s legitimately signed gives the recipient the assurance that the message was created and sent by a known person. And not only that, but it also tells the recipient that the message hasn’t been tampered with in transit.

To put it in simpler terms, a digital signature is the digital equivalent of a handwritten signature. And a significant advantage of a digital signature over a handwritten one is that it’s substantially harder to forge.

Digital signatures can be employed to authenticate:

  • Documents and files
  • Emails
  • Software

Thanks to rapid digitization all around the globe, the use of digital signatures has increased significantly. They’re being used extensively in a variety of contexts and industries, including:

  • ecommerce,
  • software distribution,
  • financial transactions,
  • contract management software, and
  • other domains where the information has greater importance and a higher probability of becoming compromised.

It’s More Than Just a Signature

Although the most common usage of digital signatures is document, software and email signing, they’re capable of so much more. They also can be used to authenticate web servers and applications, corporate email systems, etc. However, in this post, we’ll be focusing on digital signatures in the context of documents, files, and emails.

How Does a Digital Signature Work?

The foundation of a digital signature lies in public key cryptography (PKI), or asymmetric encryption. This is the same technology that’s used in SSL/TLS certificates. A digital signature is like a numerical value that is represented as a series of characters. The creation of these characters is an intricate mathematical process, and only computers can create them.

To better understand how digital signatures work, let’s explore a scenario using our friends Bob, Alice, Liam, and Ryan. Liam’s a hacker, and Bob and Alice are good friends who frequently communicate with one another. But Liam, for whatever reason, wants to disrupt their relationship. And since he’s into hacking, he thinks he can do this by altering their messages.

Bob, as he always does, sends an email to Alice. Liam, with his dangerous intentions and skills, intercepts the message and alters it in such a way that would anger Alice. Then, he sends this tampered message to Alice, who is blissfully unaware.

Alice receives the tampered message and calls Bob to express her confusion and frustration. Poor Bob, of course, has no idea what’s going on and tries to convince Alice that it wasn’t the message that he had actually sent. After a heated argument, Alice gives Bob the benefit of the doubt and decides that they should go to their friend Ryan, who’s into cyber security, for advice.

Ryan listens to both of them and instantly suggests that they should start using digital signatures to authenticate and secure their messages. Bob and Alice like the idea and decide to start using them.

As Bob is the sender, he keeps the private key, and its public key is kept with Alice. To send the message securely, Bob must encrypt the email using his public key. However, before performing the encryption process, the hash value of the email message is created by Bob’s computer. The hash value, then, is encrypted by Bob’s private key to create a digital signature.

Now, when Bob sends an email to Alice, the original message — along with the digital signature — is sent to Alice. When Alice receives it, her email client identifies that it’s been signed digitally and can be opened only upon its verification. Now, Alice’s computer decrypts the digital signature using the public key and turns it into a hash.

It also calculates the hash value of the original message and compares them both. If there’s even slightest of difference between the hash values, Alice will be notified that the message has been altered.

Types of Digital Signatures

Depending upon the platform that you intend to use, there are four types of digital signatures:

  1. Certified Signatures supported by Adobe). They indicate the identity of the author and documents signed display a unique blue ribbon near the top of the document.
  2. Approval Signatures (supported by Adobe). Approval Signatures can be implemented in a business workflow since you can embed things such as physical signatures, date, place, official seals, etc.
  3. Visible Signatures (supported by Microsoft Office). These signatures have the provision in which one or more users can digitally sign a document. They’re displayed the same way as physical signatures in a physical document.
  4. Invisible Signatures (supported by Microsoft Office). They’re equivalent to certified signatures since they validate the authenticity of the sender and the integrity of the document. A blue ribbon also indicates their use.

How Can I Digitally Sign My Emails?

Because digital signatures work via public key cryptography, you must first obtain a digital certificate from a trusted certificate authority (CA). You can, however, create your own self-signed certificate. But the recipients won’t be able to verify the authenticity of your signature with a self-signed certificate.

Once you’ve downloaded and installed a CA-issued certificate, you can quickly sign your emails using the Sign and Encrypt buttons on your mail client.

How Can I Create a Digital Signature in Adobe?

To sign your documents in Adobe, you must download Adobe Sign. This application will allow you to sign your documents very easily. Here are the steps to sign documents in Adobe:

  1. Download and install Adobe Sign.
  2. Open Adobe Sign and select the Fill & Sign option in its dashboard.
  3. Now open the document that you want to sign.
  4. Click on the Sign tool and select Add Digital Signature.
  5. Now select Cloud-Based Digital ID Certificate, then click Apply.
  6. Choose the certificate authority that you’d like to issue your document signing certificate and fill in the required information fields.
  7. Almost there! Select the Click to Sign option and enter the PIN number that you want to keep. Fill in any additional information as needed.

Nicely done! You’ve successfully signed your document.

How Can I Create an Invisible Digital Signature in MS Office?

The process of authenticating your MS Office documents is pretty straightforward. Here’s how to do it:

  1. Open the document/workbook/presentation that you want to protect.
  2. Next, click the File tab.
  3. Click Info.
  4. Select Protect Document, Protect Workbook, or Protect Presentation.
  5. Click Add a Digital Signature.
  6. Click Ok once you’ve verified the contents of your file.
  7. Now enter the purpose why you’re signing the file.
  8. Click Sign.

Once you’ve signed the document, the Signature button appears at the bottom of the document.

A Final Word

Thanks to relentless efforts of cybercriminals, the use of digital signatures has become a norm in many organizations. Many countries have already approved the use of digital signatures, and many more are expected to join. As a result, the adoption of digital signatures is expected to steadily increase.

According to a report by Data Bridge Market Research, the global digital signature market will witness a healthy CAGR of 30.2% in the forecast period of 2019 to 2026. We won’t be surprised if the actual number surpasses this number by a good margin, as protecting authenticity and integrity is of paramount importance.