A CSR or Certificate Signing request is a block of encoded text that is given to a Certificate Authority when applying for an SSL Certificate. It is usually generated on the server where the certificate will be installed and contains information that will be included in the certificate such as the organization name, common name (domain name), locality, and country. It also contains the public key that will be included in the certificate. A private key is usually created at the same time that you create the CSR, making a key pair. A CSR is generally encoded using ASN.1 according to the PKCS #10 specification.
A certificate authority will use a CSR to create your SSL certificate, but it does not need your private key. You need to keep your private key secret. The certificate created with a particular CSR will only work with the private key that was generated with it. So if you lose the private key, the certificate will no longer work.
What is contained in a CSR?
The fully qualified domain name (FQDN) of your server. This must match exactly what you type in your web browser or you will receive a name mismatch error.
The legal name of your organization. This should not be abbreviated and should include suffixes such as Inc, Corp, or LLC.
The division of your organization handling the certificate.
Information Technology IT Department
The city where your organization is located.
The state/region where your organization is located. This shouldn't be abbreviated.
The two-letter ISO code for the country where your organization is location.
An email address used to contact your organization.
The public key that will go into the certificate.
The public key is created automatically
What does a CSR look like?
Most CSRs are created in the Base-64 encoded PEM format. This format includes the "-----BEGIN CERTIFICATE REQUEST-----" and "-----END CERTIFICATE REQUEST-----" lines at the begining and end of the CSR. A PEM format CSR can be opened in a text editor and looks like the following example: