A certificate authority (CA) is a trusted organization that issues digital certificates to verify the identity of websites, servers, and other entities online. The certificates ensure that a website is genuine and secure by using encryption technology, such as SSL/TLS, to encrypt information sent via the internet. Think of a certificate authority as a digital passport office, ensuring that the identity of the website you are accessing is valid, offering secure encrypted connections.

How certificate authorities work

If you ever visit a site that uses HTTPS (like an online store or your bank website), the page shows a digital certificate issued by a certificate authority. The certificate contains:

• The website’s public key. To be used to encrypt data received by the site.
• The certificate authority's digital signature.Verifying that the certificate has been issued by a trusted source.
• The website’s domain name and other details. To authenticate the site's identity.

For encryption to work securely, the website has a corresponding private key, which is kept secure on the server.

Certificate authorities also issue document signing certificates, which are used to authenticate the identity of the sender of a document. Meanwhile, code signing certificates are used by software developers to ensure the integrity and authenticity of their code. The browser or device you are using authenticates this certificate to ensure that the site is what it claims to be, and man-in-the-middle (MITM) attacks are avoided.

Examples of certificate authorities

Several well-known certificate authorities include the following.

• Let’s Encrypt. It is one of the well-known CAs issuing free SSL certificates to websites so that it becomes easy for anyone to secure their website.
• DigiCert. It is known for issuing multiple certificates with extended validation for business organizations.
• GlobalSign. A trustworthy company offering different digital certificates to ensure secure communication for any size and type of business.
• Comodo. Offers affordable SSL certificates and other security features.

Why are certificate authorities important?

Certificate authorities exist because they are crucial to website security. They ensure that the sites you are visiting are legitimate, which secures your data from being decrypted and your privacy from being breached.

Without a certificate authority and without the trust established by root certificates, there would be no way of trusting that a website is what it claims to be, leaving users open to phishing attacks and other types of cyber threats. Certificate chains, such as intermediate certificates connecting the website's certificate to a trusted root certificate, further strengthen trust. Apart from the certificate, the site’s own private key guarantees that only the intended recipient can decrypt the data sent.

How to choose a certificate authority

When choosing a certificate authority, consider the following.

• Trustworthiness. The CA should be recognized by major web browsers and devices for the sake of compatibility.
• Support for your needs. Some CAs offer basic certificates, while others offer extended validation (EV) certificates for more secure transactions.
• Price. There are also free CAs, such as Let's Encrypt, and paid ones for those requiring additional validation or special services.
• Warranty and customer support. A good certificate authority should have good customer service and a warranty to cover any security problems that may arise.

How to check if your website has a valid certificate

This is how to ensure your website is using a valid certificate.

• Look for HTTPS in the URL. Websites with an SSL/TLS certificate will have "https://" at the beginning of their web address.
• Check for a padlock icon. Most browsers will display a padlock icon in the address bar if the website is secured with a certificate.
• Click on the padlock icon. You can view details about the certificate, including which certificate authority issued it and its expiration date.

FAQs about certificate authorities

Why do I need a certificate authority for my website?

A certificate authority helps protect your website by verifying your identity and ensuring that data transmitted between your website and users is secure. This builds trust with visitors and protects them from security threats.

What’s the difference between SSL and TLS certificates?

SSL (Secure Sockets Layer) and TLS (Transport Layer Security) are protocols that encrypt data between a website and its users. While SSL is the older version, TLS is the modern version, and both are typically bundled under the name "SSL certificates."

How do I get a certificate from a certificate authority?

To get a certificate, you typically need to generate a certificate signing request (CSR) and submit it to a certificate authority. Once they verify your details, they will issue a certificate for your website.

Can a certificate authority be hacked?

While certificate authorities are highly secure, no system is immune to attacks. That's why it’s essential to choose a well-established and reputable certificate authority with strong security measures in place.

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