How do digital signatures work?

by May 20, 2022Blog, Contracts & Signatures, Solutions

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Digital signatures have become a popular way to add a layer of security to sensitive documents, such as e-commerce transactions. They’re particularly useful when you have to send sensitive documents to different people. Digital signatures work by attaching a digital identifier to the document. When the document is signed, its digital signature is added to the document. The digital signature cannot be altered without being known as the original document.

If you’ve ever sent a document to a colleague, you’ve probably encountered digital signatures. Your colleague might have signed a document as verification that the document comes from them. How do digital signatures work? The basics are simple. You digitally sign a document using a digital signature key. This key is non-reusable, meaning that it can only be used once. In this guide, we’ll explore what a digital signature key is, how to create a digital signature key in different operating systems, and how to use a digital signature key in your environment.

What is a digital signature key?

A digital signature key is a set of cryptographic keys used to sign documents. A digital signature key is always associated with a private key and a public key. This key pair is the foundation of the digital signature process. The private key is the key that’s associated with the public key. The private key must remain private because it enables the person who holds it to sign documents. However, anyone who holds the public key can verify a digital signature.

How to create a digital signature key

The process of creating a digital signature key varies depending on the operating system you’re using. For Windows, you can create a digital signature key by using the Microsoft Authenticode tool. For Linux and Mac OS, you’ll need to use the OpenSSL tool. Once the tool is installed, use it to create the key pair. The steps you take to create a digital signature key depend on the platform you’re using. But, generally, you’ll start by listing the names and extensions of the files you’d like to sign with the digital signature key. Next, you’ll create the public/private key pair with the key pair generator.

How to use a digital signature key

To use a digital signature key, send the public key associated with the key to the person you’d like to sign a document. Then, the person who holds the private key can sign the document by using the public key. When a person signs a document using the public key, the key pair creates a digital signature. To verify a digital signature, you can use the private key to decrypt the public key. Then, you can use an authenticity verifier to check that the public key matches the private key. This verification process ensures that the person who signed the document is who they say they are. To make digital signatures more secure, you can use multiple levels of digital signatures. The level of security you have depends on the number of levels and the strength of each level.

How digital signatures work

Electronic signatures are a way to sign documents without having to print, sign, and scan them. The technology has been around for years, but we’ve only recently seen it being used everywhere, from the office to the doctor’s office. Paperless transactions are easy and efficient, but they’re also safe and have legal protection. In fact, digital signatures are regarded by the courts as legally binding. But how can a computer-generated signature be legally binding? How do they work?

Digital signatures use encryption to verify the person’s identity by signing a document. A unique set of numbers and letters is attached to the document, which is relayed to the recipient as soon as the document is signed. If anyone tries to tamper with the document or if someone else attempts to sign it after it’s been signed once, this encrypted string of numbers/letters will change and show that something about the document has changed—and you’ll know not to open it. This encryption is similar to how your bank keeps your information safe when you log in online. When you enter your username and password for your account, an algorithm runs all those numbers against the bank’s records of usernames and passwords.

Here are the different ways that digital signatures work:

1. Digitally signed documents can be verified.

A digital signature can be verified by anyone. Let’s say your friend sends you a PDF of the Best Chocolate Chip Cookie Recipe, and I digitally sign it. To verify that the document was sent by me, you can check my public key against the digital signature attached to the recipe. If these two match, then I sent the recipe to you. In other words, my public key (which anyone can have) confirms that I am indeed who I say I am — a chocolate chip cookie expert.

You can also verify a digital signature with a certificate authority (CA), the third party. When generating your first digital signatures for documents, it’s best practice to get these certificates from trusted CAs like Comodo. By checking their database of certificate holders, you’ll be able to find out whether or not someone is truly who they say they are when they sign their documents.

2. You can tell who signed a document.

Digital signatures are based on public-key cryptography, and in order to perform a digital signature, you must have a certificate. Certificate authorities (CA) issue certificates, which contain public keys and other information about the signer. The certificate authority can revoke certificates if they discover that the signer acted in bad faith or any of the number of reasons why a CA might revoke a certificate. In this way, a digital signature is like an electronic seal—it creates trust when someone uses it on something as innocuous as an e-mail message.

3. Timestamps are built into the signature.

Once you’ve added your signature to the document, it will be applied with a timestamp. What’s a timestamp? A timestamp is a note that records when and where the signature was made. It not only serves as proof of identity but it also provides essential information about when the document was signed. That way, even if you need to verify that a document was signed at an earlier date (for example, if you’re looking over something like your annual tax return), there’ll be no question about which version of the file is which—or when each version was created. It’s important to note here that this type of a timestamp isn’t quite the same as those imprinted by notaries or other live signatures that are witnessed in person; notary stamps are more likely to include some sort of verification from a third party (like a lawyer or witness) along with details about their own identification information and commission expiration date.

4. Digital signatures help prevent fraud.

Digital signatures provide irrefutable proof that a specific individual signed a document. They are often used to protect against fraud and forgery, and they even prevent charges from being made to the originally-signed document.

With traditional ink signatures, you have no way of knowing whether or not the signature was forged; it’s entirely possible that the document could’ve been tampered with in any number of ways. Using digital signatures is much safer, as they allow you to keep track of who signs what documents. Digital signatures also help preserve the authenticity of documents by attaching a unique code to each one that cannot be tampered with once it’s created (and if someone tries to change the content, everyone will know). You can be sure that no one has modified or altered the contents during their journey from your desk drawer into your inbox!

5. You can use a digital signature on any kind of file or document.

For example, you can sign a PDF document as easily as you might sign a paper copy. You can also use digital signatures on images and text files, Word documents, Excel spreadsheets, and PowerPoint presentations—all common types of documents shared online. There are even digital signatures for YouTube videos and blog posts. In other words: whatever it is you need to sign, there’s a way to do it digitally!

6. Digital signatures are unique to each user.

Digital signatures are unique to each user. A digital signature guarantees that the document comes from you and no one else, so you can see that it was signed by the correct sender. A digital signature is calculated by using a private key generated for each signer based on a certificate specific to that signer. When you receive a document signed with a particular certificate, you know who signed it.

7. The document’s contents cannot be altered after it’s been signed.

The digital signature is tied to the contents of the document. If anyone were to alter it in any way after a document has been signed, the signature would no longer work. This is an important security measure because it prevents other people from changing your documents after electronically signing them.

8. Digital signatures don’t last forever.

A digital signature is like a password for your document. Whoever has the password can verify that the document hasn’t been tampered with since you signed it, and if you change your mind about sending it, you can revoke access to the document.
However, unlike a regular physical signature, digital signatures have expiration dates that you can set. You can also revoke them. Here’s how they work:

  • After a certain amount of time passes, no one will be able to read or open the document once it’s been sent and signed unless they have permission to do so—which is only if you allow it by extending their access period or giving them permission again through an updated signature.
  • If someone got into the file while they still had access and attempted to remove or change your signature, that person would have to send it back around as a separate file because yours wouldn’t match up anymore. That could be useful in an office environment where multiple people are reviewing documents during different stages before finalizing them with signatures from all parties involved.
  • If something comes up after sending out your initial batch of signed documents (such as finding out there was an error), you’ll need to revoke everyone’s permissions and send out new signed versions without that mistake.

9. Digital signatures don’t require a unique piece of hardware to create or install.

Digital signatures don’t require a unique piece of hardware to create or install. In fact, you can use any electronic device to sign forms or documents, including mobile devices like smartphones and tablets, and desktop computers. You can even add a digital signature remotely if you’re not physically in the same room as the person who is going to receive it. There are plenty of digital signature services available, some of which are free, allowing you to sign documents using your computer or handheld device.


As you may already know, digital signatures are encrypted. This means that they’re more secure than a traditional paper document, but it also means that you can’t just open a digitally signed document with any old software.

If the digital signature contains only an image of your handwritten signatures, such as a PDF or Word file, then you can use any software to open it—you just won’t be able to verify its authenticity using that software. If the digital signature is attached to code or software, that software must be verified to run properly. Suppose the digital signature is attached to an email message (which is common when sending sensitive documents). In that case, the recipient’s email client must support verifying digital signatures for them to see whether or not the message was altered by someone else. Finally, suppose the digital signature is part of a form filled out on a website and submitted electronically. You’ll need special browser extensions to ensure the form has been submitted properly and hasn’t been tampered with while en route.

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