How do SSL certificates work?

An SSL certificate is a data file that is hosted on the webserver of a website. It facilitates making the SSL handshake possible to ensure a secure and encrypted transmission pathway is created between the requester and the webserver. To know more about the SSL handshake which makes the communication b/w a browser and the web server secure, please click here.

SSL certificates are issued by a Certification Authority (CA) and contain the following information:

1. Domain information of the host
2. The entity that the certificate is issued to
3. CA information which signed the certificate
4. Issue and Expiration date of the certificate
5. The public key

Examples of certification authorities (CAs) are Digicert, Certbot, etc. All the popular browsers recognize a list of these CAs and trust the certificates signed by them. When an SSL certificate is installed in the webserver, it is tied up with the root certificate of the CA using an intermediate certificate. The combination of the web server certificate, intermediate certificate, and root certificate is known as a certificate chain. This helps in establishing the credibility of the SSL certificate.

Once the browser connects to the web server, the SSL certificate is provided to the browser with which it verifies the correct domain of the webserver, checks if the SSL certificate is valid based on its expiration date, and takes the public key to perform the SSL handshake and use it for encrypting the data to be communicated with the web server.

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