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.
Mar 31, 2018 Generate public key and store into a file. It is a simple one liner command to generate a public key from a private key, so lets say our private key is named â[email protected]â and we want to generate the public key and name it âauthorizedkeysâ. Below is the command to do this. OpenSSL can generate several kinds of public/private keypairs. RSA is the most common kind of keypair generation. Other popular ways of generating RSA public key / private key pairs include PuTTYgen and ssh.
The Commands to RunGenerate a 2048 bit RSA Key
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
This is a command that is
openssl rsa -in private.pem -outform PEM -pubout -out public.pem
The
-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:
less public.pem How are keys generated modulo hash.
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:
Generate Ssh Key Openssl Python Server
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, itâs 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. Download project 2013 with key.
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.
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Lets say you have a private/public key pair that you use to login to your server via SSH and you lose the public key, either it was deleted or corrupt and you donât want to have to regenerate a new pair what options do you have? In this post I will demonstrate how to regenerate a public key from the corresponding private key that you still have.
Generate public key and store into a file
It is a simple one liner command to generate a public key from a private key, so lets say our private key is named â[email protected]â and we want to generate the public key and name it âauthorized_keysâ. Below is the command to do this.
Now we will need to take our authorized_keys file and store it on the server, if we can currently login via SSH to our server we can use rsync over ssh to securely copy the public key to the server, Although this key is displayed to anyone who attempts to login to your server it is smart to use SSH or another secure method to copy it up to the server to ensure that the key is not tampered with while it is being transmitted.
Below is an example using rsync to copy the authorized keys file to its destination on the server and removing it from your local computer.
Lastly we will need to make sure our permissions are set properly on our public key to prevent anyone else tampering with it. We should give our key file RW, R, R permissions, below is the command to properly set permission on the key.
Ssh Generate Key Pair
Generate Ssh Key Putty
At this point we are all set to begin using our private key to login to our server again. If you have any questions about this post please leave a comment below and if this helped you at all please share it on social media!
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