What is SSL/TLS certificate

How SSL protocol works

As you know, the basis of all encoding methods is a key that helps to encrypt or read information. The SSL protocol uses an asymmetric cipher with two kinds of keys:

• Public. This is actually an SSL certificate. It encrypts data and is used when transmitting user information to the server. For example, a visitor enters his bank card number on the site and clicks on the "Pay" button.
• Private. Required to decode the message on the server. It is not transmitted along with the information, as is the case with the public key, and always remains on the server.
• For a site to handle such connections, its owner needs an SSL certificate. This is a kind of digital signature, which is individual for each platform.

What's inside an SSL certificate

An SSL certificate may contain the following important information:

• domain of the site on which the certificate is installed;
• name of the company owner;
• country, city of company registration;
• SSL certificate validity period;
• Certification Authority Information;
• Serial number of the SSL;
• SAN items (Multi-domain SSL);
• Trusted and Untrusted Certificates.

The main source of SSL certificates are trusted certification authorities or Certification authorities (CAs). These are organizations that have undeniable authority in the IT services market and use the well-known public cryptographic key. In browsers, their list can usually be found in the "Trusted Root Certification Authorities" section.

A digital signature certified by a certificate of such a center is a proof of the authenticity of the company that owns the domain name and determines the right of the owner to legally use the secret key. It is called trusted.