While Encrypting a File with a Password from the Command Line using OpenSSLis very useful in its own right, the real power of the OpenSSL library is itsability to support the use of public key cryptograph for encrypting orvalidating data in an unattended manner (where the password is not required toencrypt) is done with public keys.
The Commands to Run
Generate a 2048 bit RSA Key
- The RSA cipher used by GENERATE ENCRYPTION KEYPAIR is based on a double key encryption system: a private key and a public key. As indicated by its name, the public key can be given to a third person and used to decrypt information. The public key is matched with a unique private key.
- 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.
- Online x509 Certificate Generator. CertificateTools.com offers the quickest and easiest way to create self-signed certificates, certificate signing requests (CSR), or create a root certificate authority and use it to sign other x509 certificates. We support multiple subject alternative names, multiple common names, all x509 v3 extensions, RSA and elliptic curve cryptography private keys.
You can generate a public and private RSA key pair like this:
openssl genrsa -des3 -out private.pem 2048
That generates a 2048-bit RSA key pair, encrypts them with a password you provideand writes them to a file. You need to next extract the public key file. You willuse this, for instance, on your web server to encrypt content so that it canonly be read with the private key.
Export the RSA Public Key to a File
Usage Guide - RSA Encryption and Decryption Online. In the first section of this tool, you can generate public or private keys. To do so, select the RSA key size among 515, 1024, 2048 and 4096 bit click on the button. This will generate the keys for you.
This is a command that is
Generate A Rsa-2048 Key
openssl rsa -in private.pem -outform PEM -pubout -out public.pem
-pubout flag is really important. Be sure to include it.
Next open the
public.pem and ensure that it starts with
-----BEGIN PUBLIC KEY-----. This is how you know that this file is thepublic key of the pair and not a private key.
To check the file from the command line you can use the
less command, like this:
Rsa 2048 Encryption
Do Not Run This, it Exports the Private Key
A previous version of the post gave this example in error.
openssl rsa -in private.pem -out private_unencrypted.pem -outform PEM
The error is that the
-pubout was dropped from the end of the command.That changes the meaning of the command from that of exporting the public keyto exporting the private key outside of its encrypted wrapper. Inspecting theoutput file, in this case
private_unencrypted.pem clearly shows that the keyis a RSA private key as it starts with
-----BEGIN RSA PRIVATE KEY-----.
Visually Inspect Your Key Files
It is important to visually inspect you private and public key files to makesure that they are what you expect. OpenSSL will clearly explain the nature ofthe key block with a
-----BEGIN RSA PRIVATE KEY----- or
-----BEGIN PUBLIC KEY-----.
You can use less to inspect each of your two files in turn:
less private.pemto verify that it starts with a
-----BEGIN RSA PRIVATE KEY-----
less public.pemto verify that it starts with a
-----BEGIN PUBLIC KEY-----
The next section shows a full example of what each key file should look like.
The Generated Key Files
The generated files are base64-encoded encryption keys in plain text format.If you select a password for your private key, its file will be encrypted withyour password. Be sure to remember this password or the key pair becomes useless.
The private.pem file looks something like this:
The public key, public.pem, file looks like:
Protecting Your Keys
Depending on the nature of the information you will protect, it’s important tokeep the private key backed up and secret. The public key can be distributedanywhere or embedded in your web application scripts, such as in your PHP,Ruby, or other scripts. Again, backup your keys!
Remember, if the key goes away the data encrypted to it is gone. Keeping aprinted copy of the key material in a sealed envelope in a bank safety depositbox is a good way to protect important keys against loss due to fire or harddrive failure.
Oh, and one last thing.
If you, dear reader, were planning any funny business with the private key that I have just published here. Know that they were made especially for this series of blog posts. I do not use them for anything else.
Found an issue?
Rietta plans, develops, and maintains applications.
Learn more about our services or drop us your email and we'll e-mail you back.
Other Blog Articles Published by Rietta.com
I was recently in a meeting where a person needed to generate a private andpublic key for RSA encryption, but they were using a PC (Windows). This is somethingthat is easily done via a terminal using
ssh-keygen on Mac and Linux, however on Windows…this tool is not easily accessible to the non-technical person.
So, if anyone needs an online RSA key generator, look no further than http://travistidwell.com/jsencrypt/demo.
This directly maps to the Open Source GitHub repository found at https://github.com/travist/jsencrypt, soanyone can modify this website to make it better.
And here is an iframe of the RSA key generation tool.