Generate Public Key Using Ssh-keygen Linux

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Generate Ssh Rsa Key Pair Linux
Linux Ssh Keygen Examples
Generate Public Key Using Ssh-keygen Linux Version
Generate Rsa Key Linux

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 don’t 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 RSA Key Generate DSA Key. DSA is less popular but useful public key algorithm. DSA keys can be generated by specifying key types with -t dsa $ ssh-keygen -t dsa Set Key Size. Keys have different size for different purposes. Bigger size means more security but.

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 ‘user@myserver.key’ and we want to generate the public key and name it ‘authorized_keys’. Below is the command to do this.

Command Breakdown:

‘ssh-keygen -y’ : tells the prorgram ssh-keygen to output a public key

‘-f user@myserver.key’: references the key file user@myserver.key to generate the public key from

‘> authorized_keys’: instead of printing the output to the console redirect the output (public key) to a file named ‘authorized_keys’

Copy public key to your server

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.

Generate Ssh Rsa Key Pair Linux<table><tbody><tr><td><div><div>2</div><div>4</div><div>6</div></div></td><td><div><div><span>user</span><span>@</span><span>workstation</span><span>:</span><span>~</span><span>$</span><span>rsync</span><span>-</span><span>avz</span><span>--</span><span>remove</span><span>-</span><span>source</span><span>-</span><span>files </span><span>authorized_keys </span><span>user</span><span>@</span><span>remote_server_ip_address</span><span>:</span><span>/</span><span>home</span><span>/</span><span>user</span><span>/</span><span>.</span><span>ssh</span><span>/</span><span>authorized_keys</span></div><div><span>test</span></div><div><span>sent</span><span>95</span><span>bytes </span><span>received</span><span>43</span><span>bytes</span><span>92.00</span><span>bytes</span><span>/</span><span>sec</span></div><div><span>user</span><span>@</span><span>workstation</span><span>:</span><span>~</span><span>$</span></div></div></td></tr></tbody></table><p>At this point our public key file is on our server where it is supposed to be in our users ‘.ssh’ directory.</p><h2>Set proper permissions for public key</h2><p>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.</p><div><textarea wrap='soft' readonly='>user@server:~$ chmod 644 /home/user/.ssh/authorized_keys user@server:~$

2	user@server:~$chmod644/home/user/.ssh/authorized_keys

Generate Public Key Using Ssh-keygen Linux

Linux Ssh Keygen Examples

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!

Several tools exist to generate SSH public/private key pairs. The following sections show how to generate an SSH key pair on UNIX, UNIX-like and Windows platforms.

Generating an SSH Key Pair on UNIX and UNIX-Like Platforms Using the ssh-keygen Utility

UNIX and UNIX-like platforms (including Solaris and Linux) include the ssh-keygen utility to generate SSH key pairs.

To generate an SSH key pair on UNIX and UNIX-like platforms using the ssh-keygen utility:

Navigate to your home directory:
Run the ssh-keygen utility, providing as filename your choice of file name for the private key:
The ssh-keygen utility prompts you for a passphrase for the private key.
Enter a passphrase for the private key, or press Enter to create a private key without a passphrase:
Note:
Key generator. While a passphrase is not required, you should specify one as a security measure to protect the private key from unauthorized use. When you specify a passphrase, a user must enter the passphrase every time the private key is used.
The ssh-keygen utility prompts you to enter the passphrase again.
Enter the passphrase again, or press Enter again to continue creating a private key without a passphrase:
The ssh-keygen utility displays a message indicating that the private key has been saved as filename and the public key has been saved as filename.pub. It also displays information about the key fingerprint and randomart image.

Generating an SSH Key Pair on Windows Using the PuTTYgen Program

The PuTTYgen program is part of PuTTY, an open source networking client for the Windows platform.

Generate Public Key Using Ssh-keygen Linux Version

To generate an SSH key pair on Windows using the PuTTYgen program:

Generate Rsa Key Linux

Download and install PuTTY or PuTTYgen.
To download PuTTY or PuTTYgen, go to http://www.putty.org/ and click the You can download PuTTY here link.
Run the PuTTYgen program.
Set the Type of key to generate option to SSH-2 RSA.
In the Number of bits in a generated key box, enter 2048.
Click Generate to generate a public/private key pair.
As the key is being generated, move the mouse around the blank area as directed.
(Optional) Enter a passphrase for the private key in the Key passphrase box and reenter it in the Confirm passphrase box.
Note:
While a passphrase is not required, you should specify one as a security measure to protect the private key from unauthorized use. When you specify a passphrase, a user must enter the passphrase every time the private key is used.
Click Save private key to save the private key to a file. To adhere to file-naming conventions, you should give the private key file an extension of .ppk (PuTTY private key).
Note:
The .ppk file extension indicates that the private key is in PuTTY's proprietary format. You must use a key of this format when using PuTTY as your SSH client. It cannot be used with other SSH client tools. Refer to the PuTTY documentation to convert a private key in this format to a different format.
Select all of the characters in the Public key for pasting into OpenSSH authorized_keys file box.
Make sure you select all the characters, not just the ones you can see in the narrow window. Foxit reader license. If a scroll bar is next to the characters, you aren't seeing all the characters.
Right-click somewhere in the selected text and select Copy from the menu.
Open a text editor and paste the characters, just as you copied them. Start at the first character in the text editor, and do not insert any line breaks.
Save the text file in the same folder where you saved the private key, using the .pub extension to indicate that the file contains a public key.
If you or others are going to use an SSH client that requires the OpenSSH format for private keys (such as the ssh utility on Linux), export the private key:
1. On the Conversions menu, choose Export OpenSSH key.
2. Save the private key in OpenSSH format in the same folder where you saved the private key in .ppk format, using an extension such as .openssh to indicate the file's content.