May 17, 2019  We can generate ssh key pair on Unix using ssh-keygen utility. This comes under openssh in all Unix flavour Run the ssh-keygen ssh-keygen -b 2048 -t rsa rsa: it is the algorithm for generating the public -private key pair 2048: it is bit size ssh-keygen -b 2048 -t rsa Generating public/private rsa key. Re: SSH 1024 bit keys vs. 2048 bit keys Never mind, it turned out to be a number of mis-steps on both sides that looked like the problem was the keys.

An SSH key is a form of authentication in the SSH protocol. It is similar to a password, but allows for authentication without entering in a password or any manual input. SSH keys generally speaking are more secure, and convenient than password authentication.

Command Line

If you currently have access to SSH on your server, you can generate SSH keys on the command line using the ssh-keygen utility which is installed by default on our servers. Run it on your server with no options, or arguments to generate a 2048-bit RSA key pair (which is plenty secure).

You will be prompted to select a file for the key pair. The default directory for SSH keys is ~/.ssh with the private key named id_rsa and the public key named id_rsa.pub. By using the default file names, the SSH client will be able to automatically locate the keys during authentication so it is strongly recommended to not change them. You can use the default by pressing the Enter key.

If /home/USER/.ssh/id_rsa or a key of the name you chose already exists, you will be prompted to overwrite the keys. If you do overwrite the existing keys, you will not be able to use them to authenticate anymore.

After you have selected the file for the key pair, you be will be prompted to enter a passphrase to encrypt private key file. Encrypting the private key with a passphrase is optional, but it will improve security the keys. If you enter a passphrase you will have to provide each it time you use the key. You can press the Enter key to not use a passphrase; we strongly recommend the use of a passphrase with SSH keys.

A public and private key will now be generated.

WHM


You can generate SSH key pairs for root in WHM >> Home Security Center >> Manage root's SSH Keys.



Click Generate a New Key to get started.


There are several fields on this page: Key Name, Key Password, Key Type, and Key Size.

The default Key Name is id_rsa. Keys are generated in /root/.ssh/ so the default key name would create a private key in /root/.ssh/id_rsa, and a public key in /root/.ssh/id_rsa.pub. Using the default name will allow SSH clients to automatically locate the keys so it is strongly recommend you use the default name (simply leave the field blank or fill it with id_rsa).


The Key Password encrypts the private key file using a password to add an extra layer of security. The password must be provided each time the key is used for authentication to decrypt the private key. The Password Strength field indicates how strong your password is. 0 indicates a very weak password, and 100 indicates a very strong password. Click Password Generator to have a strong password generated for you.


Key Type and Key Size are RSA and 2048 by default, and are secure enough for most purposes so these can be left alone.

Click Generate Key to generate the SSH key pair. WHM will then display the location of the key.

PuTTY

PuTTY is an open Windows SSH client. You will need to have the PuTTYgen utility installed to generate an SSH key pair. PuTTYgen is included in Windows installer on the Download PuTTY site, but you can download it separately if you installed PuTTY without its extra utilities. See Connect using Putty to a Linux Server to learn more about PuTTY.

Open PuTTYgen.

The Parameters at the bottom can be adjusted to affect how secure the key is, but the default options are plenty secure for most purposes.

If you're satisfied with the parameters, click Generate in Actions to generate the key pair.

You may be asked to 'generate some randomness by moving the mouse over the blank area' to generate the key. The randomness is used to generate your keys securely, and make it difficult to reproduce them.


Once the key is generated, you will see the public key in PuTTYgen.

The Key passphrase field sets a password used to decrypt the private the key. This field is optional, and the private key will not be encrypted if it is omitted.Using a passphrase increases the security of your SSH keys, and we strongly recommend setting one.

Be sure to save both the public and private keys on your local machine so they can be used by PuTTY for authentication in the future by clicking the Save public key and Save private key buttons.

If you don't use a passphrase, it will prompt you to confirm before allowing you to save the private key. The private key will be saved as a .ppk file. The public key isn't given an extension by default, but .pub is a common extension for public key files. It can be saved as a .txt file as well as the public key file only stores the public key in plain text.

Command Line

If you currently have access to SSH on your server, you can upload the key over the command line.

Retrieve the contents of the public key. If the key was created in the default location, this can be done by outputting the contents of ~/.ssh/id_rsa.pub.

The output will look similar to the following:

Open the (and create if it doesn't exist) ~/.ssh/authorized_keys file using a text editor such as nano, pico, or vim.

If you had to create the ~/.ssh/ directory, or the authorized_keys file, you need to verify the permissions are correct, or you won't be able to login.


Paste the public key at the bottom of the file, and then save and close the file.

Alternatively, you can append the public key to ~/.ssh/authorized_keys with a single command.

You can use the cat command if the public key is stored in a file.

If the public key is not stored as a file on the server, you can use the echo command.

Be sure to include the entire public key in quotes after echo.

Once the public key is added to the authorized_keys file, you should be able to login using your SSH keys.

WHM

You can import an existing SSH key for root in WHM >> Home Security Center >> Manage root's SSH Keys.

Click Import Key.

The next page has a few fields to fill in.

You need to name the SSH key in the Choose a name for this key field. The default key name is id_rsa. Using the default name will allow SSH clients to automatically locate the keys so it is strongly recommend you use the default name (simply leave the field blank or fill it with id_rsa).

If you are importing a PPK (PuTTYgen key) file, enter its password (if applicable) in the Private key passphrase text box.

Paste the public key into the appropriate box, but do not paste the private key into the box; private keys should always remain on the servers that generated them.

Click Import.

WHM will display the name of the keys imported, and you should now be able to authenticate over SSH using the key.

The default name for SSH key pairs is id_rsa, and that name will allow an SSH client to locate the key automatically. When an SSH key pair doesn't use the default name, you will need to specify the name of key used.


Introduction

Secure Shell (SSH) is an encrypted protocol used by Linux users to connect to their remote servers.

Generally, there are two ways for clients to access their servers – using password based authentication or public key based authentication.

Using SSH keys for authentication is highly recommended, as a safer alternative to passwords.

This tutorial will guide you through the steps on how to generate and set up SSH keys on CentOS 7. We also cover connecting to a remote server using the keys and disabling password authentication.

1. Check for Existing Keys

Prior to any installation, it is wise to check whether there are any existing keys on the client machines.

Open the terminal and list all public keys stored with the following command:

The output informs you about any generated keys currently on the system. If there aren’t any, the message tells you it cannot access /.ssh/id_*.pub , as there is no such file or directory.

2. Verify SSH is Installed

To check if thw package is installed, run the command:

If you already have SSH, the output tells you which version it is running. Currently, the latest version is OpenSSH 8.0/8.0p1.

Note: Refer to our guide If you need to install and enable SSH on your CentOS system.

Steps to Creating SSH keys on CentOS

Step 1: Create SSH Key Pair

1. Start by logging into the source machine (local server) and creating a 2048-bit RSA key pair using the command:

2048 bit encryption

If you want to tighten up security measures, you can create a 4096-bit key by adding the -b 4096 flag:

2. After entering the command, you should see the following prompt:

3. To save the file in the suggested directory, press Enter. Alternatively, you can specify another location.

Note: If you already have a key pair in the proposed location, it is advisable to pick another directory. Otherwise it will overwrite existing SSH keys.

4. Next, the prompt will continue with:

Although creating a passphrase isn’t mandatory, it is highly advisable.

5. Finally, the output will end by specifying the following information:

Now you need to add the public key to the remote CentOS server.

You can copy the public SSH key on the remote server using several different methods:

  1. using the ssh-copy-id script
  2. using Secure Copy (scp)
  3. manually copying the key

The fastest and easiest method is by utilizing ssh-copy-id. If the option is available, we recommend using it. Otherwise, try any of the other two noted.

1. Start by typing the following command, specifying the SSH user account, and the IP address of the remote host:

If it is the first time your local computer is accessing this specific remote server you will receive the following output:

2. Confirm the connection – type yes and hit Enter.

3. Once it locates the id_rsa.pub key created on the local machine, it will ask you to provide the password for the remote account. Type in the password and hit Enter.

4. Once the connection has been established, it adds the public key on the remote server. This is done by copying the ~/.ssh/id_rsa.pub file to the remote server’s ~/.ssh directory. You can locate it under the name authorized_keys.

5. Lastly, the output tells you the number of keys added, along with clear instructions on what to do next:

1. First, set up an SSH connection with the remote user:

2. Next, create the ~/.ssh directory as well as the authorized_keys file:

3. Use the chmod command to change the file permission:

chmod 700 makes the file executable, while chmod 600 allows the user to read and write the file.

4. Now, open a new terminal session, on the local computer.

5. Copy the content from id_rsa.pub (the SSH public key) to the previously created authorized_keys file on the remote CentOS server by typing the command:

With this, the public key has been safely stored on the remote account.

1. To manually add the public SSH key to the remote machine, you first need to open the content from the ~/.ssh/id_rsa.pub file:

2. As in the image below, the key starts with ssh-rsa and ends with the username of the local computer and hostname of the remote machine:


3. Copy the content of the file, as you will need later.

4. Then, in the terminal window, connect to the remote server on which you wish to copy the public key. Use the following command to establish the connection:

5. Create a ~/.ssh directory and authorized_keys file on the CentOS server with the following command:

6. Change their file permission by typing:

7. Next, open the authorized_keys file with an editor of your preference. For example, to open it with Nano, type:

8. Add the public key, previously copied in step 2 of this section, in a new line in (under the existing content).

9. Save the changes and close the file.

10. Finally, log into the server to verify that everything is set up correctly.

Once you have completed the previous steps (creating an RSA Key Pair and copying the Public Key to the CentOS server), you will be able to connect to the remote host without typing the password for the remote account.

All you need to do is type in the following command:

If you didn’t specify a passphrase while creating the SSH key pair, you will automatically log in the remote server.

Otherwise, type in the passphrase you supplied in the initial steps and press Enter.

Once the shell confirms the key match, it will open a new session for direct communication with the server.

Although you managed to access the CentOS server without having to provide a password, it still has a password-based authentication system running on the machine. This makes it a potential target for brute force attacks.

You should disable password authentication entirely by following the outlined steps.

Note: Consider performing the following steps through a non-root account with sudo privileges, as an additional safety layer.

1. Using the SSH keys, log into the remote CentOS server which has administrative privileges:

2. Next, open the SSH daemon configuration file using a text editor of your choice:

Crack 2048 Bit Rsa Key

3. Look for the following line in the file:

4. Edit the configuration by changing the yes value to no. Thus, the directive should be as following:

5. Save the file and exit the text editor.
6. To enable the changes, restart the sshdservice using the command:

Generate 2048 Bit Ssh Key For Pc

7. Verify the SSH connection to the server is still functioning correctly. Open a new terminal window and type in the command:

Generate 2048 Bit Ssh Key Password

In this article, you learned how to generate SSH key pairs and set up an SSH key-based authentication. We also covered copying keys to your remote CentOS server, and disabling SSH password authentication.

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