SSL Certificate Checker

Web server configuration analysis and testing service for diagnosing, validating and resolving TLS/SSL certificate installation errors.

Example: www.ssl.org / wikipedia.org more info

Free online tool for test SSL security

SSL definition and history

SSL is an abbreviation and stands for Secure Sockets Layer. It is a cryptographic protocol that provides secure communication between a web server and a web browser. SSL encrypts all communication between the server and the browser, so that if anyone intercepts the communication it is unreadable.

SSL is the predecessor to TLS (another abbreviation which standas for Transport Layer Security). TLS is a more modern and secure protocol than SSL, and it is the protocol that is currently used by most websites.

Browser and server communication

When you visit a website that is using SSL, your browser will send a message to the server asking for the website's SSL certificate. The server will then send the certificate back to the browser. The browser will then verify the certificate to make sure that it is valid. If the certificate is valid, the browser will establish a secure connection with the server.

A secure HTTPS connection to a domain (website) with a valid SSL certificate from a trusted certificate authority ensures that all communication between your web browser and the website is encrypted and secure. This means that your personal information, such as your credit card number and password, cannot be intercepted and read by third parties.

Establish a secure HTTPS connection

This process is also called 'handshake' and it involves the following steps:

  • The client (web browser) sends a request to the server (website) for a secure connection. This request includes the client's supported cipher suites and the domain name of the website.
  • The server sends its SSL certificate to the client. The SSL certificate contains information about the website, such as the domain name, the organization name, and the expiration date. It also includes the server's public key.
  • The client verifies the SSL certificate. The client checks the validity of the certificate by making sure that it is issued by a trusted certificate authority and that it has not expired. The client also checks the domain name in the certificate to make sure that it matches the domain name of the website.
  • The client generates a random session key and encrypts it with the server's public key. The client then sends the encrypted session key to the server. The server decrypts the session key with its private key. The server then uses the session key to encrypt all communication between the server and the client.
  • This handshake between the server and your browser all take palce behind the scenes in hundreds of a second.

Once the handshake is complete, the client and the server can communicate securely.