What is a CSR (Certificate Signing Request)?
What is a CSR?
A CSR or Certificate Signing request is a block of encrypted text that is generated on the server that the certificate will be used on.
It contains information that will be included in your certificate such as your organization name, common name (domain name), locality, and country.
It also contains the public key that will be included in your certificate.
A private key is usually created at the same time that you create the CSR.
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.
What is a CSR and private key good for if someone else can potentially read your communications?
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?
|Common Name||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.||*.google.com
|Organization||The legal name of your organization. This should not be abbreviated and should include suffixes such as Inc, Corp, or LLC.||Google Inc.|
|Organizational Unit||The division of your organization handling the certificate.||Information Technology
|City/Locality||The city where your organization is located.||Mountain View|
|State/County/Region||The state/region where your organization is located. This shouldn’t be abbreviated.||California|
|Country||The two-letter ISO code for the country where your organization is location.||US
|Email address||An email address used to contact your firstname.lastname@example.org|
|Public Key||The public key that will go into the certificate.||The public key is created automatically|
What is a CSR’s format?
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:
-----BEGIN CERTIFICATE REQUEST-----
-----END CERTIFICATE REQUEST-----
How to generate a CSR Certificate using Openssl in Linux ?
openssl req -out <name>.csr -new -newkey rsa:2048 -nodes -keyout privateKey_<name>.key
How do I decode a CSR?
In order to decode a CSR on your own machine using OpenSSL, use the following command:
openssl req -in <name>.csr -noout -text
What is a CSR/Private Key’s bit length?
The bit-length of a CSR and private key pair determine how easily the key can be cracked using brute force methods.
A key size of 512 bits is considered weak and could potentially be broken in a few months or less with enough computing power.
If a private key is broken, all the connections initiated with it would be exposed to whomever had the key.
A bit-length of 1024 is exponentially stronger, however, it is more and more likely to be broken as computing power increases.
The Extended Validation guidelines that SSL certificate providers are required to follow (http://cabforum.org/documents.html), require that all EV certificates use a 2048-bit key size to ensure their security well into the future.
Because of this, most providers encourage 2048-bit keys on all certificates whether they are EV or not.