Home » What Is a Digital Certificate? PKI Digital Certificates Explained
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what is a digital certificate?

Learn how, when, why, and which PKI digital certificate can help keep your data, customers, and overall business secure in the online world

Digitalization has transformed our world and lives dramatically. In the last few years, we’ve seen a significant shift to online communications and transactions:

  • Many employees have moved to working remotely.
  • Consumers have started shopping online in greater numbers.
  • Businesses had to adapt managing customers and signing contracts online instead than in person.

However, the internet wasn’t designed with security in mind. Cybercriminals know this and are exploiting this vulnerability to damage end users and businesses alike. This is why digital certificates play a key role in today’s digital world, building trust, facilitating interactions, protecting millions of connected devices and its users.

Bu what is a digital certificate? In this article, we will take you on a virtual journey in the world of PKI digital certificates. You will learn how they work, why and when you should use a digital certificate, and what kind of PKI digital certificates are available out there.

PKI Digital Certificates Explained: What They and How Do They Work

To prove your identity in the real world, you can show your passport, your government-issued ID card or driver’s license because they’re accepted forms of identification. In the digital world, websites don’t have passports or driving licenses, nor do software programs have ID cards. However, there is something very similar that can be used by everyone: the PKI digital certificate.

What Is a Digital Certificate? A Digital Certificate Definition

A digital certificate, also called public key infrastructure (PKI) certificate, is an electronic form of authentication and identification that comes in the form of a small file. It uses mathematical formulas to handle a variety of functions:

  • Assert the identity of the certificate holder (organization, individual, device, etc.).
  • Encrypt and decrypt data in transit.
  • Secure data transfers and email communications, and/or
  • Attach a digital signature to software, documents, and emails.

All of this is done through the use of asymmetric encryption, which involves the use of cryptographic key pairs (or what are commonly known as public and private keys). A public key (which is available to everyone) encrypts information, whereas a private key (which you keep secure) decrypts it.

Many digital certificates are issued by publicly trusted certificate authorities (CAs). Each certificate typically includes information about the key holder (i.e., name, public key and its expiration date), a digital signature, and the name of the CA that issued the certificate.

Digital certificates can also be created and managed locally by a private entity, or what’s known as a private CA. A typical example is when a company creates its own private digital certificates restricted to use internally within its organization and internal network(s).

Public vs Private Digital Certificates

Public certificates are used by the majority of people however, depending from the environment in which they’re utilized, there may be some occasions where private certificates may come in handy.

Public CA CertificatesPrivate CA Certificates
Issued ByA publicly trusted certificate authority (such as DigiCert or Sectigo).Your own local certificate authority (private CA).
Issued ToAnyone who pays the fee.System and users within your organization only.
Uses and ApplicationsTo secure data that transmits between clients and websites/web apps on public-facing servers.To secure data on internal networks and devices connected to those networks.
Pros– The majority of applications, servers, and clients are already configured to recognize publicly trusted CAs.
– Companies and users trust public CAs more than private ones.
– Increased security as you issue certificates only to trusted members of your organization.
– Lower managing costs if issued for a high number of users for client authentication.
ConsHigh managing costs if issued for a high number of private users for client authentication.– Time and resources invested.
– These certificates don’t work on public-facing networks.

Your best choice is to use a digital certificate from a public CA for applications that involve your public-facing servers and resources. It’s trusted automatically by the major browsers and operating systems and makes

If you are working within your own organization and users, using the more secure private digital certificate can be a cost-effective option. This will ensure that access to your private services will be restricted only to the members of your organization.

Five Common Types of Digital Certificates

There are five main types of digital certificates that you can use for external or internal applications. Let’s see in more details the differences among them and their key features.

1. SSL/TLS Certificate (Secure Socket Layer/Transport Layer Security/)

The SSL/TLS certificate, also known as a website security certificate, is installed on the server to ensure that the communications between the server (i.e., mail server, app, LDAP or web) and the client are secure and encrypted. For example, all websites with a URL starting with https (instead of http) are using SSL certificates.

http vs https

There are many types of SSL certificates in terms of what they cover:

  • Single domain SSL certificate: Affordable strong encryption for a single domain/subdomain. Mostly used by blogs, forums and basic websites.
  • Multi domain SSL certificate: Strong encryption for up to 250 domains (depending on the provider). The certificate can be installed on multiple servers.
  • Wildcard SSL certificate: Specific for the protection of all of the single-level subdomains for a specific URL.
  • Multi domain wildcard SSL certificate: As above, but it can encrypt many individual domains and their respective subdomains.

Certificates Validation Level

SSL/TLS certificates have three different validation levels, offering three distinctive levels of security and authentication:

  • Domain Validation (DV),
  • Organizational Validation (OV), and
  • Extended Validation (EV).

These digital certificates not only certify that the website is encrypted, they also provide your users with more verified information about your organization. This increases trust, allowing the user to have a better idea of the level of safety of the website they’re visiting.

Let’s have a look to each of them and compare their features:

Domain Validation (DV)Organizational Validation (OV)Extended Validation (EV)
Level of Authentication and Identity ValidationLow. Anyone can get it, even a malicious bot.Moderate validation. Business certificate with nine validation checks.Highest validation. Business certificate with a high number of validation checks.
What It ValidatesThat you own or control the domain of the website for which you requested a certificate.This basic business validation verifies you own or control the domain but also verifies additional information about your organization.This extended business validation goes beyond what an OV certificate verifies to ensure that the certificate requestor is legitimate and so is their organization.
Certificate Issuance ProcessThis is an automated process. The CA sends an email to the domain owner listed in the WHOIS database to confirm that the buyer is the legitimate owner of the URL.The domain owner must provide to the CA up-to-date documentation proving that the company exists and that it’s a legitimate legal entity. The company will manually verify this information using a mix of provided and external resources. This is a process that can take 1-3 days.The certificate can be issued only by a select number of CAs undergoing a yearly audit before being approved. The CA must follow strict procedures to validate the requesting company’s ownership, organizational information, physical location, legal existence, registration number. This is an extensive manual vetting process that can take several days.
How Is It Visualized in The Browser?You’ll see a padlock security icon in the browser near the URL bar.  When clicking on the padlock near the URL, no additional organizational details are shown as this certificate validates only the domain.You’ll see a padlock security icon in the browser near the URL bar. You can find additional validated company information within the SSL/TLS certificate subject details.You’ll see a padlock security icon in the browser near the URL bar. When clicking on the padlock, you’ll see verified organizational information displayed there. You’ll see additional verified organization information in the certificate Subject details.
What Websites Should Use ItBlogs, testing domains, personal websites. Basically, anything that doesn’t collect any type of personal information.Small e-commerce websites, websites managing personal or sensitive information. This level of validation should be the minimum for websites that collect sensitive information.Government sites, global brands, organizations, institutions.

2. Code Signing Certificate

Different from the previously mentioned SSL certificates, software developers and publishers use code signing certificates to validate their software, executables, or other files by asserting their identity and providing file integrity assurance. Basically, a code signing certificate authenticates the publisher’s identity and confirms that the file or software it’s genuine and that hasn’t been tampered with. It’s especially useful for companies using third-party websites to distribute their software.

Like the TLS certificate, code signing certificates rely on using public and private keys. If you’re considering using a code signing certificate, there are two options to choose from:

  • Standard code signing certificate: The publisher’s digitally signs the code and the end-user’s client uses the publisher’s public key to verify its identity on the backend. If confirmed, during the download or installation, the user will visualize the publisher’s organization details instead of an “Unknown Publisher” warning message. The private key is stored on the developer’s workstation.
unknown publisher
  • Extended validation code signing certificate: With the EV code signing certificate, all major browsers and operating systems, including Microsoft Smart screen filter, will immediately trust the software. As a result, no warning message like the one above will be shown to the user. There is also no need for the developer to store its private key on its network as a physical token is needed to sign the code.

If you want to know more about code signing certificates, check this article How Does a Code Signing Certificate Works?.

3. Document Signing Certificate

A document signing certificate enables you to digitally sign many types of files, including Microsoft Office and PDFs. This will allow you to ensure that your document won’t be changed when sent to another recipient. How?
Once you have received your certificate from a trusted CA, you just have to follow a few simple steps (depending on the software you use) to sign the document.

Once your digital signature is appended to the document, you can send it to your intended recipient. When the recipient receives the file, their software will automatically compare the signature with the one in your certificate. If they match, it means the document hasn’t been modified and the recipient can view it without any worries. If they don’t match, the recipient will receive a warning that the file could be dangerous or harmful.

tip svg iconTip: The signing and warning processes may be slightly different from one software to the next. However, using a document signing certificate will always enable you and your recipients to immediately spot any unauthorized changes to your signed documents. Cool, isn’t it?

4. Client Authentication Certificate

A client authentication certificate, also called digital ID, is used to restrict access to databases by ensuring only authorized users can log in to them. It uses PKI for authentication to verify the identity of a person or a device so they can establish a secure, encrypted connection to your web apps or other secure resources. It’s pretty popular nowadays, as remote access and cloud computing are quickly becoming the norm.

5. IoT Device Certificate

The IoT device certificate and PKI together play a key role in the ever-expanding worlds of IoT and IT security. They enable you to protect every connected device securing its authentication, data integrity and encryption from cybercriminals.

In addition, with the IoT device certificate, there is no need to use a password: once the device is registered as authorized by the IT admin, it connects to the network using the SSL/TLS protocol. The device can then identify itself and other devices through the public key, and exchange data.

Thanks to end-to-end encryption and rock-solid authentication, the IoT device certificate becomes part of your organization’s a multi-layer protection, ensuring hacker-proof secure communication between the IoT devices and the network, dramatically reducing data leaks and the risk of breaches.

Now that we know what PKI digital certificates are and how they work, we can move on to the next question.

What Is a Digital Certificate Used For?

In general, digital certificates are used to confirm the identity of people and electronic assets on the internet. They allow for secure, encrypted online communications and are often used to protect online transactions. The following are a few examples of the most common digital certificate use cases:

  • Email signing and encryption: These days, many people work remotely. As such, they sometimes have to send sensitive data or private information (e.g., bank account details or a confidential presentation) via email. How do they do it securely? By using a digital certificate, of course! An email signing certificate enables you to both sign and encrypt your email contents and attachments by using your recipient’s public key. The recipient with the related private key will be able to decrypt it automatically, keeping everything safe from prying eyes.
  • Secure web communications: You’ve finally found a website selling the raspberry pi you were looking for at an exceptionally low price! You don’t know the website though, how can you be sure that it will be safe to share your credit card information? The digital certificate can help you! Ask yourself the following questions:
    • Does the website URL start with https? If so, then the website is using an SSL certificate (meaning your connection is secure).
    • How do you know if the website or organization is legitimate? Click on the padlock to view the information about the company owning the website. If it’s using at least an OV certificate, you’ll be able to check some verified company information.
  • Software and executable signatures: When users download your software, does it pop up an “Unknown publisher” warning? If so, that’s not good because it makes your software appear untrustworthy. Avoid the hassle altogether by signing your software with an EV code signing certificate.

Secure, authenticated access: In a world where hackers are always trying to find new ways to steal credentials, a more secure authentication method like using a client authentication certificate in lieu of passwords can be a valuable solution. It’s safe and supported by all major browsers. It allows you to gain access to secure resources without ever having to enter a password. These certificates also can be stored or carried in physical hardware tokens and smart cards.

  • IoT: In a connected world, the PKI digital certificate is very important to secure the data and network access of internet of things devices (e.g., connected appliances, wearable health monitors, smart home security systems, just to name some).
  • Secure messaging: Did you know that some messaging apps like Signal use PKI digital certificates to ensure end-to-end encryption?

And we could continue but, there is still one unanswered question: why should it matter for me? And this is exactly what we’re going to find out next.

Why Digital Certificates Matter to Your Business and Customers

Digital certificates are a practical and valuable resource to protect your business and your users from cybercriminals, above all when taking into account the latest threats statistics.

The 2021 Midyear Cybersecurity Report shows that, only in the first six months this year, TrendMicro has identified and blocked more than 40 billion dangerous emails, malicious files, and URL threats. Can a PKI digital certificate help in these cases? In most of them, yes. But the benefits of digital certificates don’t stop here.

Midyear Cyber Security Report

I’m a User, Why Is a Digital Certificate So Important For Me?

If you are an internet user, and I guess you are as you’re reading this article, you’re also a potential target for cybercriminals. The digital certificates can help you, but they can do much more than that!

  • Security and privacy: Digital certificates enable you to encrypt communications and/or communication channels (emails, logins, online banking activities, etc.), protecting your data and ensuring that the information will only be seen by the intended other party.
  • Confidentiality: Digital certificates will help you to check that the person or company you’re communicating with is really who it claims to be so that you share your sensitive information only with trusted people or organizations.
  • Data integrity: How can you be sure that someone isn’t going to intercept your data on a website while it’s in transit? Once again, the digital certificate will ensure that when you send it, it will be delivered to the intended recipient without tampering.
  • Access management: Do you want to ensure that a document will only be accessed by a certain person or group of people? Now you can! All you have to do is encrypt the file and select the level of access.
  • Transaction receipt: Now, this is an interesting one. When you send an encrypted email, you’ll ensure automatically that neither the sender nor the recipient will be able to deny receiving or sending the email. This can come in handy sometimes…

Useful right? I guess you’re starting loving digital certificates now! But, what if you’re a business owner? What are the benefits for you?

I’m a Business Owner, Why Is a Digital Certificate So Important For My Company?

Let’s have a look to how digital certificates can contribute to the success of your business in a competitive, dangerous, digital world.

Security (Documents and Data Protection)

In 2021, organizations experienced the highest average cost of data breach in 17 years, growing from $3.86 million to $4.24 million. Compromised credentials were responsible for 20% of the breaches as described by IBM’s Cost of a Data Breach Report 2021.

Cost of Data Breach Report

Digital certificates can help you secure your data online. Encrypting communications avoids that your sensitive information is phished or stolen. With the usage of SSL/TLS certificates, you can ensure that the data of the customers visiting your website are secure. And last but not least, managing and storing documents digitally eliminates the risk of physical documents being lost or destroyed.


Digital certificates are easy to manage and can guarantee a high level of security to small and large businesses alike. To make things even easier, there are now many solutions available to help you automatically manage the issuance, renewal and storage of your company’s digital certificates.

Organizational Identity and File Integrity Assurance

When sending files over the internet, a digital certificate allows you to validate the file’s author identity and, at the same time, ensure its integrity.


Norton’s 2021 Life Lock Cyber Safety Insights Report Global Results data found out that 62% of surveyed adults find it difficult to determine if the information they see online comes from a credible source.

Cyberlock Safety Insights Report

And a survey made in 2019 by PandaSecurity on 1,000 people in the U.S. confirmed the importance of a secure URL (HTTPS) as a credibility factor when shopping online (chosen by a third of the surveyed people).

What Makes Website Credible

As we’ve seen earlier in this article, SSL/TLS digital certificates can help eliminate these doubts with your users and make your website more credible in their eyes. And other types of digital certificates can help you provide identity and integrity assurances regarding other areas of digital communications. More credibility will result in higher trust and increased revenue.

Brand Reputation

As mentioned before, a lack of identity verification can have disastrous consequences not only moneywise but also on your brand’s reputation. It just has to happen once. With digital certificates, you can:

  • Validate your business identity.
  • Prove to your customers that you’re exactly who you say you are. (Remember when we talked about domain validation and extended validation earlier? Using certificates with OV validation as a minimum can help.)
  • Confirm and prove the legitimacy of your website.
  • Prove to the customers that the information they share is safe (SSL).
  • Secure the access to your network.

All this will help you build customer trust.


Last but not least, digital certificates help you remain compliant with several key regulations, including:

  • The EU security standard PSD2 (payment service directive): The regulation ensures that the payments across the EU are safe, easy, and efficient, requiring a greater level of security through PSD2 compliant digital certificates and two-factor authentication.
  • Electronic Identification, Authentication and Trust Services (eIDAS): eIDAS simplifies and standardizes digital IDs, electronic and advanced signatures, qualified digital certificates and other proof of authentications for use within the European Union. Once again, compliance to this regulation is ensured by digital certificates issued by a CA.
  • Digital Signature Standard (DSS): The DSS requires all departments and agencies of the U.S. government to protect sensitive information through digital signatures and private and public key usage. When the sender sends a message to a recipient, the recipient can use the public key to verify the sender’s digital signature.
  • Payment Card Industry Data Security Standard (PCI DSS): This global relation applies to every business that collects, processes, or in any way otherwise touches credit card information for any transactions. SSL/TLS digital certificates and keys are essential to protecting sensitive cardholder data and transactions while they are in transit.
  • General Data Protection Regulation (GDPR): Its requirements to protect sensitive information can only be addressed by using SSL/TLS certificates and encryption.
  • California Consumer Privacy Act (CCPA): Data privacy and protection are at the core of this regulation. Both can be achieved through the use of digital signatures and identity verification, thus, the use of digital certificates.

These are just a few of the reasons why more and more organizations choose to use digital certificates. Let’s explore another growing area where using digital certificates can add to your security…

Digital Certificates Key Role in IoT

The number of IoT connected devices is constantly growing. A report from IOT Analytics forecasts that there will be more than 27 billion IoT device connections by 2025.

Global IOT Market Forecast

IoT implementations require:

  • A trusted device identity.
  • Integrity of data and software running on the device.
  • Confidentiality.
  • The possibility for all devices to connect from any location to any device in a secure way.

All these requirements can be covered and addressed through the usage of digital certificates and the PKI infrastructure enabling secure authentication, encryption and code signing.

Final Thoughts on What Is a Digital Certificate

Hopefully, this article has answered your questions on digital certificates and has helped you better understand what a digital certificate is and why it’s so important for companies and users alike.

We’ve learned that companies that provide strong identity for their software can:

  • Differentiate their products.
  • Increase visibility.
  • Prevent fraud.
  • Mitigate widespread attacks.

No matter who you are and what you do, digital certificates are the way to secure your activities in the digital world: unknown/untrusted sources are never safe!

We’ve now reached the end of our journey, but now you can start your own in the world of PKI digital certificates! A whole new secure internet world is waiting for you. What are you waiting for? Get your digital certificate now!