If you don't have access to a certificate authority (CA) for your organization and want to use OpenSearch for non-demo purposes, you can generate your own self-signed certificates using [OpenSSL](https://www.openssl.org/){:target='\_blank'}.
You can probably find OpenSSL in the package manager for your operating system.
On CentOS, use Yum:
```bash
sudo yum install openssl
```
On macOS, use [Homebrew](https://brew.sh/){:target='\_blank'}:
```bash
brew install openssl
```
## Generate a private key
The first step in this process is to generate a private key using the `genrsa` command. As the name suggests, you should keep this file private.
Private keys must be of sufficient length to be secure, so specify `2048`:
```bash
openssl genrsa -out root-ca-key.pem 2048
```
You can optionally add the `-aes256` option to encrypt the key using the AES-256 standard. This option requires a password.
## Generate a root certificate
Next, use the key to generate a self-signed certificate for the root CA:
Change `-days 30` to 3650 (10 years) or some other number to set a non-default expiration date. The default value of 30 days is best for testing purposes.
- The `-x509` option specifies that you want a self-signed certificate rather than a certificate request.
- The `-sha256` option sets the hash algorithm to SHA-256. SHA-256 is the default in later versions of OpenSSL, but earlier versions might use SHA-1.
Follow the prompts to specify details for your organization. Together, these details form the distinguished name (DN) of your CA.
## Generate an admin certificate
To generate an admin certificate, first create a new key:
```bash
openssl genrsa -out admin-key-temp.pem 2048
```
Then convert that key to PKCS#8 format for use in Java using a PKCS#12-compatible algorithm (3DES):
Follow the prompts to fill in the details. You don't need to specify a challenge password. As noted in the [OpenSSL Cookbook](https://www.feistyduck.com/books/openssl-cookbook/){:target='\_blank'}, "Having a challenge password does not increase the security of the CSR in any way."
Just like the root certificate, use the `-days` option to specify an expiration date of longer than 30 days.
## (Optional) Generate node and client certificates
Follow the steps in [Generate an admin certificate](#generate-an-admin-certificate) with new file names to generate a new certificate for each node and as many client certificates as you need. Each certificate should use its own private key.
If you generate node certificates and have `plugins.security.ssl.transport.enforce_hostname_verification` set to `true` (default), be sure to specify a common name (CN) for the certificate that matches the hostname of the intended node. If you want to use the same node certificate on all nodes (not recommended), set hostname verification to `false`. For more information, see [Configure TLS certificates]({{site.url}}{{site.baseurl}}/security-plugin/configuration/tls#advanced-hostname-verification-and-dns-lookup).
If you already know the certificate details and don't want to specify them as the script runs, use the `-subj` option in your `root-ca.pem` and CSR commands:
If you compare this string to the ones in `opensearch.yml` above, you can see that you need to invert the order of elements and use commas rather than slashes. Enter this command to get the correct string:
For information about adding and using these certificates in your own setup, see [Docker security configuration]({{site.url}}{{site.baseurl}}//opensearch/install/docker-security/) and [Configure TLS certificates]({{site.url}}{{site.baseurl}}/security-plugin/configuration/tls/).
For more information about what this command does, see [Apply configuration changes]({{site.url}}{{site.baseurl}}/security-plugin/configuration/security-admin/).
Depending on your settings in `opensearch_dashboards.yml`, you might need to add `root-ca.pem` to your OpenSearch Dashboards node. You have two options: disable SSL verification or add the root CA.
