Digital Certificate

May 20, 2023

A digital certificate, also known as a public key certificate, is a digital document issued by a Certificate Authority (CA) that verifies the identity of the owner of a public key. It is used to establish trust between two parties communicating over the internet by ensuring that the public key belongs to the person or organization claiming to own it.

Digital certificates are typically used for secure communication between web servers and clients in order to protect sensitive information such as credit card details or login credentials. They play a crucial role in online security by ensuring that data is transmitted securely and that communication is not intercepted or tampered with by malicious actors.


The purpose of a digital certificate is to provide a secure and trustworthy method of verifying the identity of an entity or individual online. When a website is secured with a digital certificate, it displays a padlock icon in the browser’s address bar, indicating that the website is authenticated and that data transmitted between the website and the user is encrypted.

Digital certificates are also used for other purposes such as authenticating software and devices, securing email communication, and establishing secure Virtual Private Networks (VPNs).


When a user visits a secure website, their web browser initiates a secure connection with the web server using the HTTPS protocol. The web server then presents its digital certificate to the user’s browser, which checks the certificate for validity and ensures that it is issued by a trusted CA.

The user’s browser then uses the public key contained within the certificate to encrypt the data being transmitted to the web server. The web server can then use its private key to decrypt the data and process the user’s request.

Digital certificates are also used in email communication to ensure that messages are sent and received securely. In this case, a digital certificate is used to encrypt the email message and verify the identity of the sender.

In addition to securing communication between web servers and clients, digital certificates are also used to authenticate software and devices. For example, digital certificates can be used to verify the authenticity of a software update before it is installed on a user’s computer.

Types of Digital Certificates

There are several types of digital certificates, each with a different level of security and validation:

Domain Validated Certificates (DV)

Domain Validated Certificates are the most basic type of digital certificate and are used to verify the ownership of a domain name. These certificates are typically issued within a few minutes and do not require extensive validation of the requester’s identity.

Organization Validated Certificates (OV)

Organization Validated Certificates are used to verify the identity of a business or organization. These certificates require more extensive validation than DV certificates, including verification of the organization’s legal status and physical address.

Extended Validation Certificates (EV)

Extended Validation Certificates are the highest level of digital certificate and are used to provide the most secure and trustworthy method of verifying the identity of a website owner. In addition to validating the requester’s identity, these certificates display the organization’s name in the browser’s address bar along with a green padlock icon.

Certificate Authorities

Certificate Authorities (CAs) are organizations that issue digital certificates to website owners and other entities. CAs are trusted third-party organizations that are authorized to issue digital certificates and are responsible for ensuring that the certificate holder’s identity is verified.

There are several well-known CAs, including Comodo, Symantec, and DigiCert. Each CA has its own set of validation requirements and pricing structures for issuing digital certificates.


Digital certificates can be revoked if they are compromised or if they become invalid for any reason. When a certificate is revoked, the CA adds the certificate to a Certificate Revocation List (CRL) or Online Certificate Status Protocol (OCSP) server, which informs web browsers and other applications that the certificate is no longer valid.