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With a secure shell (SSH) key pair, you can create virtual machines (VMs) in Azure that use SSH keys for authentication, eliminating the need for passwords to sign in. This article shows you how to quickly generate and use an SSH public-private key file pair for Linux VMs. You can complete these steps with the Azure Cloud Shell, a macOS or Linux host, the Windows Subsystem for Linux, and other tools that support OpenSSH.

Easeus data recovery wizard 12.9 key generator. Note

VMs created using SSH keys are by default configured with passwords disabled, which greatly increases the difficulty of brute-force guessing attacks.

For more background and examples, see Detailed steps to create SSH key pairs.

Generate 4098 Bit Key Generate 4096 Bit DSA Key. RSA is very old and popular asymmetric encryption algorithm. It is used most of the systems by default. There are some alternatives to RSA like DSA. We can not generate 4096 bit DSA keys because it algorithm do not supports. Generate 2048 Bit Key. The default key size for the ssh-keygen is 2048 bit. We can also specify explicitly the size of the key like below. When enabling the service, be sure to fully secure SSH first. I will cover some of the basics briefly, but this is not meant to be a guide on securely running an SSH server. Since Kali comes with pre-generated SSH keys, to make it more secure, the first thing we will do is generate new ones. To backup the original keys first as a precaution use. Step 3: Change Kali default ssh keys to avoid MITM attack. At this point you will have openssh-server installed on Kali Linux and enabled at runlevel 2,3,4 and 5. But now we got a problem. Every Linux system that you install via a CD or DVD.

For additional ways to generate and use SSH keys on a Windows computer, see How to use SSH keys with Windows on Azure.

Supported SSH key formats

Azure currently supports SSH protocol 2 (SSH-2) RSA public-private key pairs with a minimum length of 2048 bits. Other key formats such as ED25519 and ECDSA are not supported.

Create an SSH key pair

Use the ssh-keygen command to generate SSH public and private key files. By default, these files are created in the ~/.ssh directory. You can specify a different location, and an optional password (passphrase) to access the private key file. If an SSH key pair with the same name exists in the given location, those files are overwritten.

The following command creates an SSH key pair using RSA encryption and a bit length of 4096:

If you use the Azure CLI to create your VM with the az vm create command, you can optionally generate SSH public and private key files using the --generate-ssh-keys option. The key files are stored in the ~/.ssh directory unless specified otherwise with the --ssh-dest-key-path option. The --generate-ssh-keys option will not overwrite existing key files, instead returning an error. In the following command, replace VMname and RGname with your own values:

Provide an SSH public key when deploying a VM

To create a Linux VM that uses SSH keys for authentication, specify your SSH public key when creating the VM using the Azure portal, Azure CLI, Azure Resource Manager templates, or other methods:

If you're not familiar with the format of an SSH public key, you can display your public key with the following cat command, replacing ~/.ssh/id_rsa.pub with the path and filename of your own public key file if needed:

A typical public key value looks like this example:

If you copy and paste the contents of the public key file to use in the Azure portal or a Resource Manager template, make sure you don't copy any trailing whitespace. To copy a public key in macOS, you can pipe the public key file to pbcopy. Similarly in Linux, you can pipe the public key file to programs such as xclip.

The public key that you place on your Linux VM in Azure is by default stored in ~/.ssh/id_rsa.pub, unless you specified a different location when you created the key pair. To use the Azure CLI 2.0 to create your VM with an existing public key, specify the value and optionally the location of this public key using the az vm create command with the --ssh-key-values option. In the following command, replace VMname, RGname, and keyFile with your own values:

If you want to use multiple SSH keys with your VM, you can enter them in a space-separated list, like this --ssh-key-values sshkey-desktop.pub sshkey-laptop.pub.

SSH into your VM

With the public key deployed on your Azure VM, and the private key on your local system, SSH into your VM using the IP address or DNS name of your VM. In the following command, replace azureuser and myvm.westus.cloudapp.azure.com with the administrator user name and the fully qualified domain name (or IP address):

If you specified a passphrase when you created your key pair, enter that passphrase when prompted during the login process. The VM is added to your ~/.ssh/known_hosts file, and you won't be asked to connect again until either the public key on your Azure VM changes or the server name is removed from ~/.ssh/known_hosts.

If the VM is using the just-in-time access policy, you need to request access before you can connect to the VM. For more information about the just-in-time policy, see Manage virtual machine access using the just in time policy.

Next steps

• For more information on working with SSH key pairs, see Detailed steps to create and manage SSH key pairs.

• If you have difficulties with SSH connections to Azure VMs, see Troubleshoot SSH connections to an Azure Linux VM.

What is an SSH key?

While an SSH key is an access credential, it is technically a cryptographic key. SSH uses public-key cryptography (or asymmetric cryptography) and challenge-response authentication as a more secure method of authentication. Using SSH keys allows you to be authenticated to the remote server without sending your password over the network.

Generate Ssh Key Linux

SSH keys are generated in pairs (public and private), that are mathematically related, but not identical. They work together to authenticate when logging into an SSH server. The public key is used to encrypt and the private key is used to decrypt. When the client attempts to connect to the remote server, the server will verify that the client has a private key that corresponds with the authorized public key. If the private key is verified to match the public key, the client is authenticated and a shell session is launched.

The public key can be shared, because it is infeasible to compute the private key based on the public key.

Generate New Ssh Key Mac

The private key is not shared, and must be secured, so it is advisable to store it in encrypted form. This will require that a passphrase is entered when the private key is required. The passphrase is not transmitted over the network because it is only needed to decrypt the private key on the local system.

*Note: While setting a passphrase is an optional step, it is strongly recommended. If the private key was compromised, the unauthorized user would be able to assume that identity on the SSH server.

Key generation: Windows and Linux

[Windows]

Since Windows doesn’t have a native SSH client, PuTTygen will be used to generate the keys.

*Note: PuTTy and PuTTyGen can be downloaded from http://www.chiark.greenend.org.uk/~sgtatham/putty/download.html

To create the key pair, follow these steps:

Open PuTTygen and select the desired parameters:

Type of key to generate: SSH-2 RSA [recommended]

At least 2048 for the number of bits in a generated key

Click on the “Generate” button

In the area below the progress bar, move the mouse around to generate random data needed to generate the key, until the process completes

In the next step, enter and confirm a passphrase

*Note:Set this to something memorable, because you will need it to log in.

Save the Keys

Click on the “Save public key” button and the “Save private key” button and select a secure location to save them

[Linux]

To create the key pair, use the following command:

ssh-keygen -b 2048 -t rsa

[-b 2048] is used to specify the desired key length

[-t rsa] specifies that RSA keys are to be generated (Use powers of two if you choose to increase the key length

When prompted, enter the location to store the keys, or press enter to accept the default location:

Enter file in which to save the key (/home/user/.ssh/id_rsa):

At this point, you will be prompted to enter, and confirm a passphrase:

Enter passphrase (empty for no passphrase):

Enter same passphrase again:

*Note:Set this to something memorable, because you will need it to log in.

The SSH keygen will complete, and display the locations of the keys, the key fingerprint, and the keys random art image.

[Configure the server]

Now that the keys are created, we will configure OpenSSH on the Kali system, and save the public key.

As root, issue the following command:

apt-get install openssh-server

To enable the ssh server, issue:

service ssh start

To prevent changes after restart, issue the following commands to alter the runlevels, in this order:

update-rc.d ssh remove

update-rc.d -f ssh defaults

service ssh restart

service ssh status

Next, create the following directory, set permissions, and copy the key.

Issue the following commands:

mkdir ~/.ssh

chmod 700 ~/.ssh

nano ~/.ssh/authorized_keys

Copy the public key that was created in PuTTygen to this file, as one line:

That file must be write/readable only by that user, so enter

chmod 600 ~/.ssh/authorized_keys

[Put it all together]

Attach and use the key

Launch PuTTy and specify the destination, and port:

Under category on the left, select “SSH”, then “Auth”, and click the “Browse“ button

Navigate to the location of the private key, and select it

Test login

Click “Open”

A PuTTy Security Alert will popup, indicating that the host key is not cached in the registry.

*Note: It is a good idea to quickly compare the keys before adding it to the cache.

Click “Yes”

Ssh Generate Key Pair

Enter the passphrase for the key

What Are Ssh Keys

You should now be connected