Understanding the Different Types of Digital Certificates
You may not be aware of this, but digital certificates comprise a significant portion of your online connections. Whether you are connecting to a Wi-Fi network, a website, or a different server within your organization, digital certificates facilitate that connection. They come in many different forms, from web server connection certificates to User certificates, so it is essential to understand the different types and how to interact with them. Most of you may be familiar with SSL/TLS (Secure Sockets Layer/Transport Layer Security) certificates from your own experience. Still, many more come into play in important ways when using the Internet. Let’s take a closer look at the various types of certificates.
What Is a Digital Certificate? A digital certificate is an electronic credential that binds a public key to an identity, such as a website, device, user, or piece of software, and is signed by a trusted Certificate Authority. The four most common types are SSL/TLS, user/device, code signing, and CA certificates, each securing a different kind of trust relationship.
Executive Summary
This article covers the four most common digital certificate types, SSL/TLS, User/Device, Code Signing, and CA certificates, how symmetric and asymmetric encryption underpin them, a side-by-side comparison table, a glossary of related terms, a decision tree for choosing the right certificate type, and a practical deployment checklist for keeping each type properly issued and protected.
Digital Certificate Types
The most used and well-known certificates are SSL/TLS certificates. Also utilized throughout the Internet are User or Device Certificates, Code Signing Certificates, and CA certificates. These are some of the most commonly used certificates across various organizations and infrastructures that you are likely to encounter. The importance of understanding these certificates comes from the trust they provide to users and different systems. These certificates secure the basis of trust on the Internet. It is essential to understand that all these certificates will utilize some form of encryption in their processes.
The first and simplest version of encryption we will likely discuss regarding certificates is symmetric encryption. Symmetric encryption is less commonly used today, as it is less secure than its counterpart, asymmetric encryption. Symmetric encryption utilizes a single key for both encryption and decryption. As you can see, this is an extremely unsafe method of securing communications, as each end-user requires access to this key to encrypt or decrypt the message, which would allow them to use this key to sign messages as if they were the owner of the key. For this reason, symmetric encryption is more commonly used for tasks such as encrypting large amounts of data, as opposed to encrypting direct communication.
The other method of encryption is asymmetric encryption. With this method of encryption, two keys are generated and mathematically linked: a private and a public key. The public key is used to encrypt messages, while the private key is used to decrypt these messages. This is the most common method of encryption, as anyone in the world can use the public key, while the private key is accessible only to the key’s creator. Now that we have a bit of a better understanding of what the two different types of encryption are, let’s take a look at the different digital certificate types. The first certificate type we will discuss is the SSL/TLS certificate.
SSL/TLS Certificates
SSL/TLS certificates secure communications between an end-user and a server, whether that be a web server, mail server, LDAP server, or other similar services. An SSL/TLS certificate is most commonly used to encrypt data between a user and a website, making it an ideal scenario to explain how these certificates work.
If you look at the webpage you are reading this blog on and look at the left side of the search bar, you should see an icon next to the URL. Clicking this icon will allow you to view the SSL/TLS certificate associated with our webpage if you select the lock option. This certificate ensures that you have a secure connection to the webpage, where all communications between you and the website are protected from potential threat actors who may attempt to intercept them.
These certificate types utilize asymmetric encryption to safeguard the data exchanged between the user and the webpage. SSL/TLS certificates not only protect communications between a user and a webpage, but also authenticate the identity of the website’s owner. One other note to make about SSL/TLS certificates is the different terminology used for validation. These different types of certificates are called Domain Validated, Organization Validated, and Extended Validation. The DV certificate needs the least level of identity for verification, whereas the EV needs the most.
User/Device Certificates
Another commonly seen type of certificate is a User or Device certificate. These are extremely similar certificates, which is why we put them together in this section. You may also hear these referred to as client certificates. These types of certificates identify a device or user within an organization. Most commonly, we see these types of certificates used in businesses to allow different devices or users to access specific data or information within the business. Most organizations will only allow specific data to be accessed by those users who need to have access to that data to complete their job. To restrict access to this data to only specific users, user/device certificates are utilized.
When attempting to access the information, the server storing the data will request the certificate from the user or device and then verify that the user or device is authorized to access the data. If they identify as someone who can access the data, then they are allowed onto the server. If not, they are blocked from accessing that data. Think of these certificates as a more advanced version of using a password to access data or services in a business. You may also see these certificates used in two-factor authentication (2FA) schemes.
Code Signing Certificates
Another important type of certificate, especially for developers, is a code signing certificate. Code signing is a process where a piece of code or software is run through a hashing algorithm, which then outputs a unique hash digest. This hash digest is then encrypted using a private key, and the encrypted hash, along with the certificate associated with the private key, is combined to form a signature for that piece of code. This signature identifies the developer of the code and ensures that the end-user using that code or software can trust that the software does not contain any malware.
These code signing certificates are extremely vital to keep secure, as if an attacker gained access to the certificate or the key associated with it, they could create software embedded with malware and distribute it to users, who would believe your organization signed it. This is why a recent CA/Browser Forum ruling stated that code signing private keys must be secured within Hardware Security Modules (HSMs) to protect the keys from threat actors.
CA Certificates
The final type of digital certificate we will discuss is the Certificate Authority (CA) certificate. The CA certificate is a vital component of an organization’s infrastructure, as most organizations will have a Public Key Infrastructure (PKI). The PKI operates by utilizing a Root CA, which is maintained offline at all times. The only time it should be used is when a new Issuing CA is being put online. The Root CA will sign the Issuing CA’s certificate, allowing the Issuing CA to generate certificates for users, such as user, device, or code signing certificates, for them to use. These CA certificates are crucial because they are considered the root of trust in a Public Key Infrastructure (PKI).
If an attacker can steal the Root or Issuing CA certificate and sign any certificates they want, then they can access any data within the network that they want, even though they shouldn’t be able to.
Comparison Table: The Four Digital Certificate Types at a Glance
| Certificate Type | Binds Identity Of | Common Use Case | Key Protection Requirement |
|---|---|---|---|
| SSL/TLS Certificate | A server (website, mail server, LDAP server) | Encrypting traffic between a user and a server; authenticating the server’s identity | Private key stored securely on the server; DV/OV/EV validation level chosen per risk |
| User/Device Certificate | An individual user or a specific device | Restricting access to internal data or systems; often paired with 2FA | Private key stored on the user’s device or a smart card/HSM |
| Code Signing Certificate | A software publisher or developer | Proving software hasn’t been tampered with and identifying its source | Private key must be stored in an HSM per CA/Browser Forum requirements |
| CA Certificate | A Certificate Authority itself (Root or Issuing) | Signing and issuing all other certificate types in a PKI | Root CA kept offline; Issuing CA private key protected in an HSM |
Glossary of Digital Certificate Terms
These terms come up most often when discussing digital certificate types:
| Term | Definition |
|---|---|
| Digital Certificate | An electronic credential that binds a public key to an identity and is signed by a trusted Certificate Authority. |
| SSL/TLS Certificate | A certificate that secures communications between a user and a server and authenticates the server’s identity. |
| Domain Validated (DV) Certificate | An SSL/TLS certificate requiring only proof of control over a domain, the lowest validation level. |
| Organization Validated (OV) Certificate | An SSL/TLS certificate requiring verification of the requesting organization’s identity, a mid-tier validation level. |
| Extended Validation (EV) Certificate | An SSL/TLS certificate requiring the most rigorous identity verification of the requesting organization. |
| User/Device Certificate | A certificate that identifies a specific user or device, often used to restrict access to internal systems or as part of two-factor authentication. |
| Code Signing Certificate | A certificate used to sign software or code, proving its origin and that it has not been tampered with. |
| CA Certificate | A certificate belonging to a Certificate Authority, used to sign and issue other certificates within a PKI. |
| Root CA | The top-level Certificate Authority in a PKI hierarchy, kept offline except when signing an Issuing CA’s certificate. |
| Issuing CA | The Certificate Authority that issues day-to-day certificates (user, device, code signing) to end entities, signed by the Root CA. |
Decision Tree: Which Certificate Type Do I Need?
- Securing a website or server connection → SSL/TLS certificate; choose DV, OV, or EV based on how much identity assurance you need to show visitors.
- Restricting internal data or systems to specific employees or devices → User/Device certificate, often combined with two-factor authentication.
- Distributing software and proving it hasn’t been tampered with → Code signing certificate, with the private key stored in an HSM.
- Standing up or maintaining your organization’s own PKI → CA certificate, with the Root CA kept offline and the Issuing CA protected in an HSM.
Certificate Deployment Checklist
- Identify which of the four certificate types the use case actually requires before requesting one.
- For SSL/TLS certificates, choose the validation level (DV, OV, EV) that matches the trust your audience needs to see.
- Store code signing private keys in a Hardware Security Module (HSM), per current CA/Browser Forum requirements.
- Keep the Root CA offline at all times except when signing a new Issuing CA certificate.
- Protect the Issuing CA’s private key in an HSM, since it signs every certificate the organization issues.
- Document which certificate templates map to which certificate type across your CA(s).
- Set up expiration monitoring and automated renewal so no certificate type is left to expire unnoticed.
- Restrict who can request each certificate type, especially code signing and CA certificates.
- Periodically audit issued certificates against this list to catch any issued from the wrong template or with the wrong validation level.
- Review key protection and access controls whenever a new certificate type is introduced into the environment.
Conclusion
As you can see, the majority of internet security is interwoven with various types of certificates to protect your online security. From User certificates to CA certificates, there is a lot to keep track of regarding digital certificates. Luckily, Encryption Consulting is here to help. At Encryption Consulting, we specialize in PKI, encryption, and certificates of all types, supporting our customers. We can help your organization design, implement, and manage your PKI, or you can use our Certificate Management Platform, CertSecure Manager.
CertSecure Manager is a one-stop solution for all your digital certificate management needs. Our platform prevents certificate outages, provides a single pane of glass for certificate management, and streamlines IT operations. To learn more about the services and products that Encryption Consulting offers, visit our website at preview.encryptionconsulting.com/.
Frequently Asked Questions
There are four common types, SSL/TLS, user/device, code signing, and CA certificates, and each secures a different trust relationship. Using the wrong type, or protecting its private key incorrectly, undermines the trust the certificate is supposed to provide.
A PKI’s Root and Issuing CA certificates are the root of trust for every certificate issued beneath them. If teams don’t understand how SSL/TLS, user/device, and code signing certificates differ, they’re more likely to misconfigure validation levels, key storage, or access controls.
A code signing key stored outside an HSM can let an attacker sign malware as if it came from your organization; a compromised CA certificate can let an attacker issue trusted certificates for anything; and an SSL/TLS certificate with the wrong validation level can undersell or overstate the trust a website deserves.
The PKI or security engineering team typically owns which certificate templates map to which certificate type, validation-level policy for SSL/TLS certificates, and key protection requirements, usually documented in the organization’s Certificate Policy (CP) and Certification Practice Statement (CPS).
A CLM platform needs to track each certificate’s type, validation level, and expiration separately, since renewal requirements and key protection rules differ significantly between an SSL/TLS certificate and a code signing certificate.
Audit issued certificates against documented templates to confirm each was issued as the intended type, with the intended validation level, and confirm that code signing and CA private keys are verified to be HSM-protected, not just assumed to be.
Expiration dates for every type, validation-level consistency for SSL/TLS certificates, HSM protection status for code signing and CA keys, and whether the Root CA has been brought online for anything other than signing an Issuing CA certificate.
Yes. Multi-CA environments need consistent certificate type and validation-level policy applied across every issuing CA, and cloud-issued certificates should be inventoried alongside on-premises ones so no certificate type is managed in a blind spot.
Treating all certificates as interchangeable, most commonly issuing an SSL/TLS-style certificate for a use case that actually needs a user/device or code signing certificate, or underestimating how strictly a code signing key must be protected.
Yes. SSL/TLS, user/device, code signing, and CA certificates all currently rely on RSA or ECC key pairs, both expected to eventually be broken by quantum computers, so organizations should begin tracking where each certificate type is used to prepare for a future migration to post-quantum algorithms.
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