Feb 13, 2006  Using OpenSSL on the command line you’d first need to generate a public and private key, you should password protect this file using the -passout argument, there are many different forms that this argument can take so consult the OpenSSL documentation about that. Keys are the basis of public key algorithms and PKI.Keys usually come in pairs, with one half being the public key and the other half being the private key. With OpenSSL, the private key contains the public key information as well, so a public key doesn’t need to be generated separately. Public keys come in several flavors, using different cryptographic algorithms. Generating Private Keys. Ed25519 isn't listed here because OpenSSL's command line utilities do not support Ed25519 keys yet. The key will use the named curve form, i.e. The only correct form, which unfortunately isn't the default form in all versions of OpenSSL. To generate private (d,n) key using openssl you can use the following command: openssl genrsa -out private.pem 1024 To generate public (e,n) key from the private key using openssl you can use the following command: openssl rsa -in private.pem -out public.pem -pubout.

1. Openssl Create Public Key
2. Openssl Generate Public Private Key
3. Generate Public Private Key Pair Using Openssl
4. Public Private Key Encryption
5. Generating A Public Private Key Using Openssl Download

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OpenSSL is a CLI (Command Line Tool) which can be used to secure the server to generate public key infrastructure (PKI) and HTTPS. This article helps you as a quick reference to understand OpenSSL commands which are very useful in common, and for everyday scenarios especially for system administrators.

Certificate Signing Requests (CSRs)

If we want to obtain SSL certificate from a certificate authority (CA), we must generate a certificate signing request (CSR). A CSR consists of mainly the public key of a key pair, and some additional information. Both these components are merged into the certificate whenever we are signing for the CSR.

While generating a CSR, the system will prompt for information regarding the certificate and this information is called as Distinguished Name (DN). The important field in the DN is the Common Name (CN) which should be the FQND (Fully Qualified Domain Name) of the server or the host where we intend to use the certificate with. Keygenerator.getinstance algorithm generate key.

The next item in a DN is to provide the additional information about our business or organization. If we purchase an SSL certificate from a certificate authority (CA), it is very important and required that these additional fields like “Organization” should reflect your organization for details.

Openssl Create Public Key

Here is a general example for the CSR information prompt, when we run the OpenSSL command to generate the CSR.

We can also provide the information by non-interactive answers for the CSR information generation, we can do this by adding the –subj option to any OpenSSL commands that we try to generate or run.

Below is an example for the –subj option where we can provide the information of the organization where we want to use this CSR.

Generating CSRs

In this section, we will cover about OpenSSL commands which are related to generating the CSR. This CSR can be used to request an SSL certificate from a certificate authority.

Generate a Private Key and a CSR

If we want to use HTTPS (HTTP over TLS) to secure the Apache or Nginx web servers (using a Certificate Authority (CA) to issue the SSL certificate). Also, the ‘.CSR’ which we will be generating has to be sent to a CA for requesting the certificate for obtaining CA-signed SSL.

Below is the command to create a 2048-bit private key for ‘domain.key’ and a CSR ‘domain.csr’ from the scratch.

The ‘–newkey rsa:2048’ is the option which we are specifying that the key should be 2048-bit using the RSA algorithm. The ’ –nodes’ option is to specifying that the private key should not be encrypted with a pass phrase. The ‘-new’ option, indicates that a CSR is being generated.

Generate a CSR from an Existing Private Key

Here we will learn about, how to generate a CSR for which you have the private key.

Below is the command to create a new .csr file based on the private key which we already have.

Generate a CSR from an Existing Certificate and Private key

Here we can generate or renew an existing certificate where we miss the CSR file due to some reason. Here, the CSR will extract the information using the .CRT file which we have.

Below is the example for generating –

Where -x509toreq is specified that we are using the x509 certificate files to make a CSR.

Generating a Self-Singed Certificates

Here we will generate the Certificate to secure the web server where we use the self-signed certificate to use for development and testing purpose.

Here, we generate self-signed certificate using –x509 option, we can generate certificates with a validity of 365 days using –days 365 and a temporary .CSR files are generated using the above information.

Viewing the Certificates Files

Please note that, CSR files are encoded with .PEM format (which is not readable by the humans). This is required to view a certificate. In this section, we can cover the OpenSSL commands which are encoded with .PEM files.

Viewing CSR Files Entires

Openssl Generate Public Private Key

The below command will be used to view the contents of the .CRT files Ex (domain.crt) in the plain text format.

Working with Private Keys

Generate Public Private Key Pair Using Openssl

In this section, will see how to use OpenSSL commands that are specific to creating and verifying the private keys.

Create a Private Key

Below is the command to create a password-protected and, 2048-bit encrypted private key file (ex. domain.key) –

Enter a password when prompted to complete the process.

Public Private Key Encryption

Verify a Private Key

Below is the command to check that a private key which we have generated (ex: domain.key) is a valid key or not

Generating A Public Private Key Using Openssl Download

If the private key is encrypted, you will be prompted to enter the pass phrase. Upon the successful entry, the unencrypted key will be the output on the terminal.

In this article, we have learnt some commands and usage of OpenSSL commands which deals with SSL certificates where the OpenSSL has lots of features. We will learn more features and usage in the future. I hope this article will help us to understand some basic features of the OpenSSL.