What is CN (Common Name)?
The Common Name (CN) is a term commonly used in the context of SSL certificates. It refers to the primary identifying information embedded within the certificate.
SSL certificates are used to establish secure connections between a client (usually a web browser) and a server. They ensure that the data exchanged during the communication remains encrypted and cannot be intercepted or tampered with.
Every SSL certificate issued has a CN field, which is typically used to specify the domain name or hostname associated with the certificate. For example, if you have a website with the domain name “www.example.com,” the CN field of the SSL certificate would usually contain “www.example.com.”
The CN serves an important purpose in the SSL handshake process. When a client connects to a server, it examines the server’s SSL certificate to verify its authenticity. During this verification, the client checks if the domain name or hostname it is trying to connect to matches the CN field in the certificate. If there is a mismatch, the client may display a warning to the user, indicating that the connection may not be secure.
It is important to note that the CN field is not exclusively limited to domain names. In some cases, particularly in local or internal networks, SSL certificates may use IP addresses or other unique identifiers in the CN field. This allows secure communication within those networks.
In recent years, there has been a shift towards using an alternative field called the Subject Alternative Name (SAN). The SAN field allows multiple domain names or hostnames to be specified, whereas the CN field only allows a single entry. The SAN field offers more flexibility and is recommended for situations where multiple domain names need to be secured under a single SSL certificate.
In conclusion, the Common Name (CN) is a crucial component of an SSL certificate, serving as the primary identifying information. It helps verify the authenticity of the certificate during the SSL handshake process. As the internet evolves, the use of the Subject Alternative Name (SAN) field is becoming more prevalent, providing greater flexibility for securing multiple domain names.
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