Nov 10, 2011 How to Generate A Public/Private SSH Key Linux By Damien – Posted on Nov 10, 2011 Nov 18, 2011 in Linux If you are using SSH frequently to connect to a remote host, one of the way to secure the connection is to use a public/private SSH key so no password is transmitted over the network and it can prevent against brute force attack. Jan 29, 2017 Create a key-based Authentication SSH connection If your Server is accessible over the Internet, you can use public key authentication instead of passwords, because SSH key authentication with password phrase is way more secure than password-only authentication, while a password can eventually be cracked with a Brute-force attack or keyloggers. Generate a new SSH public and private key pair: $ ssh-keygen -t rsa -C 'identifying comment' -f keypair “Identifying comment” can be any string that will assist in determining which key this is. “username@hostname” of the machine where you are connecting from would be a good example.
SSH keys can serve as a means of identifying yourself to an SSH server using public-key cryptography and challenge-response authentication. The major advantage of key-based authentication is that in contrast to password authentication it is not prone to brute-force attacks and you do not expose valid credentials, if the server has been compromised.
Furthermore SSH key authentication can be more convenient than the more traditional password authentication. When used with a program known as an SSH agent, SSH keys can allow you to connect to a server, or multiple servers, without having to remember or enter your password for each system.
Key-based authentication is not without its drawbacks and may not be appropriate for all environments, but in many circumstances it can offer some strong advantages. A general understanding of how SSH keys work will help you decide how and when to use them to meet your needs.
In this guide, we’ll set up SSH keys for a CentOS 7
Generate a Key Pair
- Open Terminal
You now have a public and private key that you can use to authenticate. The next step is to place the public key on your server so that you can use SSH-key-based authentication to log in.
Upload your Public Key
There are a few different ways to upload your public key
1. Using ssh-copy-id
ssh-copy-id is a utility available on some operating systems that can copy a SSH public key to a remote server over SSH.
Now try logging into the machine, with: “ssh ‘[email protected]remote_host‘ “ and check to make sure that only the key(s) you wanted were added.
2. Using Secure Copy (scp)
Secure Copy (scp) is a tool that copies files from a local computer to a remote server over SSH
Connect to your server via SSH with the user you would like to add your key to:
Create the ~/.ssh directory and authorized_keys file if they don’t already exist:
Give the ~/.ssh directory and authorized_keys files appropriate file permissions:
In terminal on your local machine, use scp to copy the contents of your SSH publickey(id_rsa.pub) into the authorized_keys file on your server.
Now you can log in to the server with your key.
3. Copying Public Key Manually
If you do not have password-based SSH access to your server available, you will have to complete the above process manually.
We will manually append the content of your id_rsa.pub file to the ~/.ssh/authorized_keys file on your remote machine.
To display the content of your id_rsa.pub key, type this into your local computer:
Note that the public key begins with ssh-rsa and ends with [email protected]
Copy that text, connect to your server via SSH with the user you would like to add your key to:
Create the~/.ssh directory and authorized_keys file if they don’t already exist:
Give the ~/.ssh directory and authorized_keys files appropriate file permissions:
Open the authorized_keys file with the text editor. Then, paste the contents of your public key that you copied in step one on a new line at the end of the file. Save and close the file.
Now you can log in to the server with your key.
Creating SSH shortcuts
Instead of using SSH on an IP address that you’ll definitely forget, you can use shortcuts instead
Add an entry for each computer you want to connect to, like this:
Now, you can ssh into the server with the shortcut.
You should now have SSH-key-based authentication configured on your server, allowing you to sign in without providing an account password.
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SSH (Secure Shell) is an encrypted protocol that is way more secure than Plain text based protocols like Telnet, however, it’s could be vulnerable if not configured properly.
We are assuming that you have root permission, otherwise, you may start commands with “sudo”.
We are going to provide 4 simple tips to get a more secure SSH protocol on your CentOS server.
Changing SSH Port
https://newmarks651.weebly.com/super-mario-maker-pc-key-generator.html. To change the Standard listening Port, you have to change the SSH Server configurations with the command below. We are using nano editor in this tutorial, you may use your own editor if you wish.
Then you need to edit the line that refers to the port number, for that you have to follow the instruction below.
Then change the port number from 22 to your preferable port (e.g. 2022) And press Ctrl +O and Ctrl +X in order to save and exit.
What you need to do is enable the newly created port through Firewall to do that follow the instructions below.
Then change the port number from 22 to your preferable port (e.g. 2022) And press Ctrl +O and Ctrl +X in order to save and exit.
What you need to do is enable the newly created port through Firewall to do that follow the instructions below.
If you run the command above and get an error that semanage command not found, run the commands below to install it.
And then run the semanage command again to allow the new port
After that you need to allow the new port through the firewall with the command below:
After that you need to allow the new port through the firewall with the command below:
Disable root logins
You’ll be adding a layer of security to your SSH server if you disable root user logins. It would be more secure to brute force attacks or in case your password is stolen.
First, you need to create a non-root user with the following instructions:
First, you need to create a non-root user with the following instructions:
Then open the ssh configuration file with your editor. (we are using nano)
Then change the Highlighted line from “PermitRootLogin yes” to “PermitRootLogin no”
Crtl+O Crtl+X
Crtl+O Crtl+X
Create a key-based Authentication SSH connection
If your Server is accessible over the Internet, you can use public key authentication instead of passwords, because SSH key authentication with password phrase is way more secure than password-only authentication, while a password can eventually be cracked with a Brute-force attack or keyloggers.
Depending on your client OS you should follow the instructions to create a pair of authentication keys.
If you are using Windows: Rsa public private key pair generator.
You have to download the Putty key generator (a.k.a Puttygen)
Here is the recommended download link:
http://www.chiark.greenend.org.uk/~sgtatham/putty/latest.html
Here is the recommended download link:
http://www.chiark.greenend.org.uk/~sgtatham/putty/latest.html
- Open PuTTYgen utility.
- For Type of key to generate, select SSH-2 RSA
- In the Number of bits in a generated key field is refer to how complicated you want your key to be, you can change the value between 2048 to 4096 for make more complicated key.
- After selecting your settings click on Generate to start Process.
- Move your mouse pointer around in the blank area of the Key section, below the progress bar (to generate some randomness) until the progress bar is full.
- A private and public key pair has now been generated.
- (Optional): it’s also recommended to set a passphrase for your key.
- Save Private and Public keys
CAUTION: be careful with choosing the path you saving the keys, if you lose them and username/password logins are disabled on your server, you might lose your access to your server.
- Then open your Putty, expand the SSH category and click on “Auth”
- In “private key file for authentication” browse your Private key.
- Finally, you should copy the Public key file in your server in this path: ~/.ssh/authorized_keys
If you are using Linux
–To generate an RSA key pair
Centos Ssh Authorized Keys
- Accept the default file location of /.ssh/id_rsa. Entering a passphrase is recommended
- The public key is written to ~/.ssh/id_rsa.pub The private key is written to ~/.ssh/id_rsa
- Copy the contents of ~/.ssh/id_rsa.pub from client system into the file ~/.ssh/authorized_keys on the Server.
- You may use “cat” command on the client side to view the file and use an editor like “nano” on the server side to modify or create the authorized_keys file.
- After all, it’s recommended to disable the Password authentication as well.
Uncomment these lines and change them refer to the line below:
Disable SSH Protocol 1
SSH has two versions that may use, SSH v1 is older and less secure than protocol SSHv2 2, it’s recommended to be disabled unless you specifically need it.
Generate Ssh Public Key Centos Server
Uncomment the line
and change it to:
Now we restart the SSH service so our new configuration take place.