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Apr 12, 2020  Now to create SAN certificate we must generate a new CSR i.e. Certificate Signing Request which we will use in next step with openssl generate csr with san command line. root@centos8-1 certs# openssl req -new -key server.key.pem -out server.csr You are about to be asked to enter information that will be incorporated into your certificate request. That generates a 2048-bit RSA key pair, encrypts them with a password you provide and writes them to a file. You need to next extract the public key file. You will use this, for instance, on your web server to encrypt content so that it can only be read with the private key. Export the RSA Public Key to a File. This is a command that is. Openssl rsa -in private.pem -outform PEM -pubout -out public.pem.

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What is a Self-Signed TLS Certificate?

Self-signed TLS certificates are suitable for personal use or for applications that are used internally within an organization. If you intend to use your SSL certificate on a website, see our guide on enabling TLS for NGINX once you’ve completed the process outlined in this guide.

Create the Certificate

1. Change to the root user and change to the directory in which you want to create the certificate and key pair. That location will vary depending on your needs. Here we’ll use /root/certs:

2. Create the certificate:

   You will be prompted to add identifying information about your website or organization to the certificate. Since a self-signed certificate won’t be used publicly, this information isn’t necessary. If this certificate will be passed on to a certificate authority for signing, the information needs to be as accurate as possible.

   The following is a breakdown of the OpenSSL options used in this command. There are many other options available, but these will create a basic certificate which will be good for a year. For more information, see man openssl in your terminal.

   • -newkey rsa:4096: Create a 4096 bit RSA key for use with the certificate. RSA 2048 is the default on more recent versions of OpenSSL but to be sure of the key size, you should specify it during creation.

   • -x509: Create a self-signed certificate.

   • -sha256: Generate the certificate request using 265-bit SHA (Secure Hash Algorithm).

   • -days: Determines the length of time in days that the certificate is being issued for. For a self-signed certificate, this value can be increased as necessary.

   • -nodes: Create a certificate that does not require a passphrase. If this option is excluded, you will be required to enter the passphrase in the console each time the application using it is restarted.

   Here is an example of the output:

3. Restrict the key’s permissions so that only root can access it:

4. Back up your certificate and key to external storage. This is an important step. Do not skip it!

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Common OpenSSL Commands with Keys and Certificates

Openssl Generate Rsa Key 4096 File

Generate RSA private key with certificate in a single command

Generate Certificate Signing Request (CSR) from private key with passphrase

Generate RSA private key (2048 bit)

Generate a Certificate Signing Request (CSR)

Generate RSA private key (2048 bit) and a Certificate Signing Request (CSR) with a single command

Convert private key to PEM format

Generate a self-signed certificate that is valid for a year with sha256 hash

View details of a RSA private key

View details of a CSR

View details of a Certificate

View details of a Certificate in DER format

Openssl Generate Rsa Key 4096 Number

Convert a DER file (.crt .cer .der) to PEM

Rsa 4096 Undo Encrypted Files

Convert a PEM file to DER