Generate Public Key And Private Key Using Openssl

11.12.202022.08.2017admin

< Cryptography

Download and install the OpenSSL runtimes. If you are running Windows, grab the Cygwin package.

With the private key, you can then generate the CSR: openssl req -new -key your-key.key -out your-request.csr If you want to extract the public key from the CSR, all examples I've seen require the private key to be present in the openssl command: openssl x509 -req -days 365 -in your-request.csr -signkey your-key.key -out your-public-key.crt. Now finally answering the initial question: As was shown above private RSA key generated using openssl contains components of both public and private keys and some more. When you generate/extract/derive public key from the private key, openssl copies two of those components (e,n) into a separate file which becomes your public key. Jul 09, 2019 Public Key Infrastructure (PKI) security is about using two unique keys: the Public Key is encrypted within your SSL Certificate, while the Private Key is generated on your server and kept secret. All the information sent from a browser to a website server is encrypted with the Public Key, and gets decrypted on the server side with the Private Key.

OpenSSL can generate several kinds of public/private keypairs.RSA is the most common kind of keypair generation.^[1]

How to: Create a public-private key pair.; 2 minutes to read; In this article. To sign an assembly with a strong name, you must have a public/private key pair. This public and private cryptographic key pair is used during compilation to create a strong-named assembly. You can create a key pair using the Strong Name tool (Sn.exe). While Encrypting a File with a Password from the Command Line using OpenSSL is very useful in its own right, the real power of the OpenSSL library is its ability to support the use of public key cryptograph for encrypting or validating data in an unattended manner (where the password is not required to encrypt) is done with public keys. Reasons for importing keys include wanting to make a backup of a private key (generated keys are non-exportable, for security reasons), or if the private key is provided by an external source. This document will guide you through using the OpenSSL command line tool to generate a key pair which you can then import into a YubiKey. It contains encoded details of the CSR and your public key. To request your SSL certificate, copy the Certificate Request text and submit it to your CA. Include all the text, including the BEGIN and END lines at the beginning and end of the text block. Install the private key. Copy the private key to the server that will host the certificate.

Other popular ways of generating RSA public key / private key pairs include PuTTYgen and ssh-keygen.^[2]^[3]

Generate an RSA keypair with a 2048 bit private key[edit]

Execute command: 'openssl genpkey -algorithm RSA -out private_key.pem -pkeyopt rsa_keygen_bits:2048'^[4] (previously “openssl genrsa -out private_key.pem 2048”)

e.g.

Make sure to prevent other users from reading your key by executing chmod go-r private_key.pem afterward.

Extracting the public key from an RSA keypair[edit]

Execute command: 'openssl rsa -pubout -in private_key.pem -out public_key.pem'

e.g.

A new file is created, public_key.pem, with the public key.

It is relatively easy to do some cryptographic calculations to calculate the public key from the prime1 and prime2 values in the public key file.However, OpenSSL has already pre-calculated the public key and stored it in the private key file.So this command doesn't actually do any cryptographic calculation -- it merely copies the public key bytes out of the file and writes the Base64 PEM encoded version of those bytes into the output public key file.^[5]

Viewing the key elements[edit]

Execute command: 'openssl rsa -text -in private_key.pem'

All parts of private_key.pem are printed to the screen. This includes the modulus (also referred to as public key and n), public exponent (also referred to as e and exponent; default value is 0x010001), private exponent, and primes used to create keys (prime1, also called p, and prime2, also called q), a few other variables used to perform RSA operations faster, and the Base64 PEM encoded version of all that data.^[6](The Base64 PEM encoded version of all that data is identical to the private_key.pem file).

Password-less login[edit]

Often a person will set up an automated backup process that periodically backs up all the content on one 'working' computer onto some other 'backup' computer.

Because that person wants this process to run every night, even if no human is anywhere near either one of these computers, using a 'password-protected' private key won't work -- that person wants the backup to proceed right away, not wait until some human walks by and types in the password to unlock the private key.Many of these people generate 'a private key with no password'.^[7]Some of these people, instead, generate a private key with a password,and then somehow type in that password to 'unlock' the private key every time the server reboots so that automated toolscan make use of the password-protected keys.^[8]^[3]

Generate a certificate signing request

Before you can install a Secure Socket Layer (SSL) certificate, you must first generate a certificate signing request (CSR). You can do this by using one of the following methods:

OpenSSL

The following sections describe how to use OpenSSL to generate a CSR for a single host name. If you want to generate a CSR for multiple host names, we recommend using the Cloud Control Panel or the MyRackspace Portal.

Install OpenSSL

Check whether OpenSSL is installed by using the following command:

CentOS® and Red Hat® Enterprise Linux®
The following output provides an example of what the command returns:
Debian® and the Ubuntu® operating system
The following output provides an example of what the command returns:

If the preceding packages are not returned, install OpenSSL by running the following command:

CentOS and Red Hat
Debian and the Ubuntu operating system

Generate the RSA key

Run the following commands to create a directory in which to store your RSA key, substituting a directory name of your choice:

Run the following command to generate a private key: /cpsc-370-aes-key-generator.html.

Create a CSR

Run the following command to create a CSR with the RSA private key (output is in Privacy-Enhanced Mail (PEM) format):

When prompted, enter the necessary information for creating a CSR by using the conventions shown in the following table.

Note: You cannot use the following characters in the Organization Name or Organizational Unit fields: < > ~ ! @ # $ % ^ * / ( ) ? . , &

Field	Explanation	Example
Common Name	The fully qualified domain name to which the certificate applies. The domain names example.com and www.example.com are distinct from each other, so be sure to submit your request for the right domain. If you are purchasing a wildcard certificate, use *.example.com.	example.com
Organization Name	The exact legal name of your organization. The Certificate Authority (CA) might seek to confirm that your organization is real and legally registered, so don’t abbreviate words that aren’t abbreviated in the organization’s legal name.	Example Inc.
Organizational Unit	The branch of your organization that is making the request.	Marketing
City/locality	The city where your organization is legally located. Do not abbreviate the city name.	San Antonio
State/province	The state or province where your organization is legally located. Do not abbreviate the state or province name.	Texas
Country/region	The two-letter International Standards Organization (ISO) abbreviation for your country.	US

Warning: Leave the challenge password blank (press Enter).

Verify your CSR

Run the following command to verify your CSR:

After you have verified your CSR, you can submit it to a CA to purchase an SSL certificate.

Windows IIS Manager

Use the following steps to generate a CSR by using Windows IIS Manager:

Note: The following steps are for IIS 8 or IIS 8.5 on Windows Server 2012.

Open IIS Manager.
In the left-hand Connections pane, click the server for which you want to generate a CSR.
In the center server Home pane under the IIS section, double-click Server Certificates.
In the right-hand Actions pane, click Create Certificate Request.

In the Request Certificate wizard, on the Distinguished Name Properties page, enter the following information and then click Next.

Field	Explanation	Example
Common Name	The fully qualified domain name to which the certificate applies. The domain names example.com and www.example.com are distinct from each other, so be sure to submit your request for the right domain. If you are purchasing a wildcard certificate, use *.example.com.	example.com
Organization Name	The exact legal name of your organization. The CA might seek to confirm that your organization is real and legally registered, so don’t abbreviate words that aren’t abbreviated in the organization’s legal name.	Example Inc.
Organizational Unit	The branch of your organization that is making the request.	Marketing
City/locality	The city where your organization is legally located. Do not abbreviate the city name.	San Antonio
State/province	The state or province where your organization is legally located. Do not abbreviate the state or province name.	Texas
Country/region	The two-letter ISO abbreviation for your country.	US

On the Cryptographic Server Provider Properties page, enter the following information and then click Next.
- Cryptographic service provider: Unless you have a specific cryptographic provider, use the default selection.
- Bit length: 2048 is the recommended bit length.
On the File Name page, enter the location where you want to save the certificate request file and then click Finish.

Generate Public Key From Private Key Openssl

After you have generated the CSR, you can submit it to a CA to purchase an SSL certificate.

Cloud Control Panel

Rackspace provides the CSR Generator for generating a CSR. The CSR Generator shows you the CSRs that you currently have and lets you create new CSRs with a simple form. After you have entered your details, the generator combines them with your private key so that you can submit the combined encoded information to a CA.

When you are done with the generator, you can return to the Cloud Control Panel by clicking any of the links in the top navigation or by going to login.rackspace.com and selecting Rackspace Cloud from the drop-down product menu in the top navigation bar.

Access the CSR Generator

Access the CSR Generator directly or through the Control Panel by using the following steps:

Log in to the Cloud Control Panel and select Rackspace Cloud from the drop-down product menu in the top navigation bar.
In the top navigation bar, click Servers > Cloud Servers.
Click the name of the server for which you want to generate a CSR.
In the right-hand Managing Your Server section under Help me with, click Generate a CSR.

The generator lists your existing CSRs, if you have any, organized by domain name.

Generate a CSR

Click Create CSR.

Enter the following information, which will be associated with the CSR:

Field	Explanation	Example
Domain Name	The fully qualified domain name to which the certificate applies. The domain names example.com and www.example.com are distinct from each other, so be sure to submit your request for the right domain. If you want to secure both domains, you can use the Alt Names field. If you are purchasing a wildcard certificate, use *.example.com.	example.com
Alt Names	(Optional) Additional domains that you want to add to the request. Each CA treats these differently, and the CA might charge for additional names. You can submit a comma-separated list.	www.example.com, secure.example.com
Email Address	(Optional) A contact email address for the certificate.	support@example.com
Organization Name	The exact legal name of your organization. The CA might seek to confirm that your organization is real and legally registered, so don’t abbreviate words that aren’t abbreviated in the organization’s legal name.	Example Inc.
Organizational Unit	(Optional) The branch of your organization that is making the request.	Marketing
City	The city where your organization is legally located. Do not abbreviate the city name.	San Antonio
State or Province	The state or province where your organization is legally located. Do not abbreviate the state or province name.	Texas
Country	Choose your country from the drop-down menu. The two-letter ISO abbreviation for your country is included in the CSR.	United States
Private Key Bit Length	Key sizes smaller than 2048 are considered insecure and might not be accepted by a CA.	1024,2048,4096
Hashing Algorithm	Both algorithms are currently trusted in mainstream browsers and offer industry recommended security. SHA-512 requires additional CPU processing.	SHA-256, SHA-512

Note: You cannot use the following characters in the Organization Name or Organizational Unit fields: < > ~ ! @ # $ % ^ * / ( ) ? . , &

After you have entered all the required information, click Create CSR.

It can take between 5 and 60 seconds for the CSR to be generated. You might need to refresh the page that displays your CSRs before the new CSR is listed.

View CSR details

When CSR has been generated, you can click its UUID (unique identifier) in the CSR list to view its details screen.

This screen displays the information that you provided, the text of the CSR, and its associated private key.

Submit the CSR to the CA

The text in the Certificate Request field is the CSR. It contains encoded details of the CSR and your public key.

To request your SSL certificate, copy the Certificate Request text and submit it to your CA. Include all the text, including the BEGIN and END lines at the beginning and end of the text block.

Install the private key