What Is SSL Certificate CN (Common Name) and Usage? – POFTUT

What Is SSL Certificate CN (Common Name) and Usage?

Common Name or CN is generally used in SSL Certificates. CN is used to define the server name which will be used for secure SSL connection. Generally this SSL certificate used to secure connection between a HTTP/S server and client browser like Chrome, Explorer, Firefox.

Common Name (CN)

Common Name is used to specify the host or server identity. When a client try to connect to a remote server like HTTP server it will first get the SSL certificate of this server. Then compare the Host name or domain name it want to connect with the Common Name provided in the SSL certificate. If they are same it will use the SSL certificate to encrypt connection.

Common name technically represented as commonName field in X.509 certificate specification. X.509 specification is used in SSL certificates which is the same.

Common Name (CN)

Common Name (CN)

We can formulate Command Name like below.

We can use following domain and host names as Common Name.

Fully Qualified Domain Name (FQDN)

Fully Qualified Domain Name or FQDN is used with Command Name interchangeable. Fully qualified name is used to define the host name in a strict manner. More details about the FQDN can be found in the following tutorial.

What is FQDN (Fully Qualified Domain Name) with Examples?

Organization Name

Organization name may be misinterpreted with the Common Name. Organization Name is the name of the organization where the IT infrastrure belongs.  Organization name shouldn’t be used for common name which will create security problems.

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SSL Certificate

SSL is a protocol used to make HTTP protocol secure by encrytpting HTTP traffic. Secure HTTP is name as HTTPS which means HTTP traffic encrypted with the SSL. SSL Certificates uses some key value pairs to define SSL Certificate properties. Common Name is important part of an SSL Certificate which will be checked against host and domain name.

Subject Alternative Name

The standard defines that single SSL Certificates can only use single Common Name. This means an SSL certificate can be used for a single Host Name + Domain Name. In order to solve this limitation Subject Alternative Name is created. SAN is used to defined multi-name or muti Common Names in SSL certificates. SAN is show as separate attribute in SSL Certificates. Here is an example Subject Alternative Name or SAN.

Subject Alternative Name

Subject Alternative Name

Check Common Name In Firefox

Click tot the lock icon which can be yellow or red.

Then we will click to the Secure Connection

Secure Connection

Secure Connection

Click More Information

Click `More Information`

Click More Information

Click View Certificate

Click `View Certificate`

Click View Certificate

Then we can see the line Common Name like below.

Common Name

Common Name

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