Putty Generate Ssh Key For Linux

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: On the Conversions menu, choose Export.
Run it on your local computer to generate a 2048-bit RSA key pair, which is fine for most uses. Ssh-keygen The utility prompts you to select a location for the keys. By default, the keys are stored in the /.ssh directory with the filenames idrsa for the private key and idrsa.pub for the public key.

PuTTY does not natively support the private key format for SSH keys. PuTTY provides a tool named PuTTYgen, which converts keys to the required format for PuTTY. You must convert your private key (.pem file) into this format (.ppk file) as follows in order to connect to your instance using PuTTY.

am a new Ubuntu 18.04 LTS user and I would like to setup ssh public key authentication. How do I set up ssh keys based authentication on Ubuntu Linux 18.04 LTS server? How do I set up SSH keys on an Ubuntu Linux 18.04 LTS server? In Ubuntu 18.04 LTS, how do I set up public key authentication?
Introduction: OpenSSH is a free and open source client/server technology for secure remote login. It is an implementation of the SSH protocol. OpenSSH divided into sshd (server) and various client tools such as sftp, scp, ssh and more. One can do remote login with OpenSSH either using password or combination of private and public keys named as public key based authentication. It is an alternative security method for user passwords. This method is recommended on a VPS, cloud, dedicated or even home-based server or laptop. This page shows how to set up SSH keys on Ubuntu 18.04 LTS server.

Ubuntu 18.04 Setup SSH Public Key Authentication

The procedure to set up secure ssh keys on Ubuntu 18.04:

Create the key pair using ssh-keygen command.
Copy and install the public key using ssh-copy-id command.
Add yourself to sudo admin account on Ubuntu 18.04 server.
Disable the password login for root account on Ubuntu 18.04.

Sample set up for SSH Keys on Ubuntu 18.04

Where,

202.54.1.55 – You store your public key on the remote hosts and you have an accounts on this Ubuntu Linux 18.04 LTS server.
Linux/macbook laptop – Your private key stays on the desktop/laptop/computer (or local server) you use to connect to 202.54.1.55 server. Do not share or give your private file to anyone.

In public key based method you can log into remote hosts and server, and transfer files to them, without using your account passwords. Feel free to replace 202.54.1.55 and client names with your actual setup. Enough talk, let’s set up public key authentication on Ubuntu Linux 18.04 LTS.

How to create the RSA/ed25519 key pair on your local desktop/laptop

Open the Terminal and type following commands if .ssh directory does not exists:
$ mkdir -p $HOME/.ssh $ chmod 0700 $HOME/.ssh
Next generate a key pair for the protocol, run:
$ ssh-keygen
OR
$ ssh-keygen -t rsa 4096 -C 'My key for Linode server'
These days ED25519 keys are favored over RSA keys when backward compatibility is not needed:
$ ssh-keygen -t ed25519 -C 'My key for Linux server # 42'

How to install the public key in Ubuntu 18.04 remote server

The syntax is as follows:
ssh-copy-id your-user-name@your-ubuntu-server-name ssh-copy-id -i ~/.ssh/file.pub your-user-name@your-ubuntu-server-name
For example:
## for RSA KEY ## ssh-copy-id -i $HOME/.ssh/id_rsa.pub user@202.54.1.55 ## for ED25519 KEY ## ssh-copy-id -i $HOME/.ssh/id_ed25519.pub user@202.54.1.55 ## install SSH KEY for root user ## ssh-copy-id -i $HOME/.ssh/id_ed25519.pub root@202.54.1.55
I am going to install ssh key for a user named vivek (type command on your laptop/desktop where you generated RSA/ed25519 keys):
$ ssh-copy-id -i ~/.ssh/id_ed25519.pub vivek@202.54.1.55

Test it

Now try logging into the Ubuntu 18.04 LTS server, with ssh command from your client computer/laptop using ssh keys:
$ ssh your-user@your-server-name-here $ ssh vivek@202.54.1.55

What are ssh-agent and ssh-add, and how do I use them on Ubuntu 18.04?

To get rid of a passphrase for the current session, add a passphrase to ssh-agent (see ssh-agent command for more info) and you will not be prompted for it when using ssh or scp/sftp/rsync to connect to hosts with your public key. The syntax is as follows:
$ eval $(ssh-agent)
Type the ssh-add command to prompt the user for a private key passphrase and adds it to the list maintained by ssh-agent command:
$ ssh-add
Enter your private key passphrase. Now try again to log into vivek@202.54.1.55 and you will NOT be prompted for a password:
$ ssh vivek@202.54.1.55

How to disable the password based login on a Ubuntu 18.04 server

Login to your server, type:
## client commands ## $ eval $(ssh-agent) $ ssh-add $ ssh vivek@202.54.1.55
Now login as root user:
$ sudo -i
OR
$ su -i
Edit sshd_config file:
# vim /etc/ssh/sshd_config
OR
# nano /etc/ssh/sshd_config
Find PermitRootLogin and set it as follows:
PermitRootLogin no
Save and close the file. I am going to add a user named vivek to sudoers group on Ubuntu 18.04 server so that we can run sysadmin tasks:
# adduser vivek sudo
Restart/reload the sshd service:
# systemctl reload ssh
You can exit from all session and test it as follows:
$ ssh vivek@202.54.1.55 ## become root on server for sysadmin task ## $ sudo -i

How do I add or replace a passphrase for an existing private key?

To to change your SSH passphrase type the following command:
$ ssh-keygen -p

How do I backup my existing private/public SSH keys

Ssh

Just copy files to your backup server or external USB pen/hard drive:

How do I protect my ssh keys?

Always use a strong passphrase.
Do not share your private keys anywhere online or store in insecure cloud storage or gitlab/github servers.
Restrict privileges of the account.

Tip: Create and setup an OpenSSH config file to create shortcuts for servers

See how to create and use an OpenSSH ssh_config file for more info.

How do I secure my OpenSSH server?

See “OpenSSH Server Best Security Practices” for more info.

Conclusion

You learned how to create and install ssh keys for SSH key-based authentication for Ubuntu Linux 18.04 LTS server. See OpenSSH server documents here and here for more info.

Puttygen aka Putty Key Generator

The key generation utility – PuTTYgen can create various public-key cryptosystems including Rivest–Shamir–Adleman (RSA), Digital Signature Algorithm (DSA), Elliptic Curve Digital Signature Algorithm (ECDSA), and Edwards-curve Digital Signature Algorithm (EdDSA) keys.

The aforementioned public-key cryptosystems principally focus on secure data transmission and digital signatures.

Although PuTTYgen collects keys in its native file format i.e. .ppk files, the keys can easily be converted to any file format. For Windows, the software interface is PuTTYgen.exe, whereas, for Linux OS the command-line adaptation is available using SSH commands.

How to use PuTTYgen?

PuTTYgen is used to generate public or private key pair for creating SSH keys. Below is the complete guidance about how to generate RSA key in the Windows operating system:

Once you install the PuTTY on your machine, you can easily run PuTTYgen. For the same, go to Windows -> Start Menu -> All Programs -> PuTTY -> PuTTYgen.
You will see the PuTTY key generator dialog box on your screen
You will find a “Generate” button in that dialog. Clicking on it will lead to generating the keys for you.
Now you will need to add a unique key passphrase in the Key passphrase and Confirm passphrase field.
Click on the “Save Public Key” and “Save Private Key” buttons to save your public and private keys.
You will see the text starting with ssh-RSA in the Public key for pasting into OpenSSH authorized_keys file field which is located at the top of the window. Copy that entire text to your clipboard by pressing ctrl+c as you will require the key to paste on your clipboard in the public key tool of control panel or directly on the cloud server.

Various Ways to Use RSA Key Pair

RSA key pair generated through PuTTYgen is used in two various ways defined as below:

To assign while creating a new cloud server
You can choose the public key from the given list of keys at the time of creating a cloud server. If you don’t find your key in that list, then first add and then assign it.
Assign to an existing cloud server
At the time of connecting to the cloud server, first of all, you need to tell PuTTY to use it for utilizing your newly created RSA key pair.

PuTTYgen being a component of the terminal emulator PuTTY does not have to be downloaded separately, hence, comes with the PuTTY .msi installation package. You can follow the simple steps to download PuTTYgen software for your system. That is the reason why you don’t need to download PuTTYgen separately. Once you download PuTTY software, you will be able to install and run PuTTYgen easily in no time. Below is the complete instruction about how to download and install PuTTY on Windows.

Apart from that, it is also integrated into third-party programs such as WinSCP installation package. Below you can find a complete PuTTYgen download and installation guide for all operating systems.

Download PuTTYgen on Windows

To download PuTTYgen the primary requisite is to acquire the copy of PuTTY installation package. For the 64-bit operating system, one must install the 64-bit version of PuTTY, i.e. putty-64bit-<version>-installer.msi.Similarly, for the 32-bit operating system, the respective 32-bit version of PuTTY, i.e. putty-<version>-installer.msi needs to be installed.

To get PuTTY, go to PuTTY Installation Download page, whereby the complete installation package will be available with setup instructions, installation guide, and download links to all other components of PuTTY such as putty.exe, pscp.exe, psftp.exe, puttytel.exe, plink.exe, pageant.exe and putty.zip.

Generate Ssh Key Github

Following the successful download of the PuTTY installation package. It is time to install the program. Go to How to install PuTTY on Windows, whereby you will find the step by step guidance for PuTTY installation for Windows operating system.

After successfully downloading and installing PuTTY on your Windows machine, you are just 2-3 clicks away to run PuTTYgen. Follow the below-given step by step guidance to run PuTTYgen:

Run PuTTYgen on Windows

To run PuTTYgen, Go to Windows -> Start Menu -> All Programs -> PuTTY -> PuTTYgen. You will see a window for the PuTTY Key Generator on your screen.

Voila! Now you can generate public or private key pair using PuTTYgen.

Download PuTTYgen for Mac

Below is the detailed guide to download PuTTYgen on Mac operating system. Mac OS has a built-in command-line SSH client known as Terminal. To utilize it, go to Finder and then opt for Go -> utilities from the top menu. After that find the terminal which supports SSH connections to remote servers.

However, to run PuTTYgen for mac, the first one must have to install PuTTY. There are multiple ways to install PuTTY, which are Homebrew or MacPorts. Both alternatives will also install the command-line of adaptations of PuTTYgen.

Ported PuTTY for Mac

Mac has the port of PuTTY which can be installed in various ways described as below:

Installation using Homebrew:
First, install the ‘brew command line’ Once installed use the below-given command to install PuTTY:-
sudo brew install putty
Installation using MacPorts:
First of all, one must install MacPorts and then use the command-line to install PuTTY. Here is the command to install PuTTY via MacPorts
sudo port install putty
Additionally, a user can also add a shortcut to the desktop by writing the following command line
–cp /opt/local/bin/putty ~/Desktop/PuTTY

However, there is an alternative way to install PuTTY on Mac OS. Cyberduck is a widely used Mac OS SSH Client. Once PuTTY installed on the Mac OS, a user can convert PuTTY derived private key format to OpenSSH.

To convert the private key to standard PEM format, type the following command –

puttygen privatekey.ppk -O private-openssh -o privatekey.pem

You can also read the guide to convert .pem file to .ppk using puttygen.

Download PuTTYgen for Ubuntu/Linux

Generate Ssh Key Linux Azure

To download PuTTYgen for Ubuntu (Linux) operating system, a user to first install PuTTY. However, in some Linux distributions, the SSH key generation tool – PuTTYgen needs to be installed independently from the PuTTY client.

For example, Debian Linux requires the below-given code to install PuTTYgen:

sudo apt install putty-tools

Generate Key Pair for Authentication in Linux

To create the key pair for authentication in Linux use the below command:-

puttygen -t rsa -b 2048 -C 'user@host' -o keyfile.ppk

Various Command Line Options of PuTTY in Linux

Below are few important command line options in the Linux operating system for PuTTY:

PuTTYgen [-t keytype [-b bits] [-q] | keyfile]
[-C new-comment] [-P]
[-O output-type | -p | -l | -L]
[-o output-file]

Options:

Add Ssh Key To Putty

Keyfile – It is the name of the existing key file to read at the time of changing the current key.
–t keytype – The command specifies the type of key to creating. Its acceptable values are RSA and dsa.rsa1.
-b bits – This command specifies a total number of bit in a particular key. 1024 is the perfect size for DSA key, while 2048 or 4096 are the perfect size for RSA keys.
–q – The command suppresses the message about progress at the time of key generation.
-C new-comment – The command will specify the comment to describe the key. It can be used for the new and/or existing key. Key operation is not affected by a comment. However, it is used to recognize the key owner, it’s not reliable completely as any value can be applied to it.
–P – Using the command will update the passphrase of a key. Passphrase helps to encrypt the private key. As passphrase can’t add or update on a command line, it prompts a new passphrase tool to alter it.
–old-passphrase-file – The old password of the key remains in this file. The command is used when the key is protected by a passphrase.
–new-passphrase file – This command prompts the new passphrase of the key. It comes in the action either at the time of generating a new key or while applying –P command to change the passphrase.
-O output-type – This command defines what to give in output. By default, the private key is the output.

Generate Ssh Key Linux Github

Thus, above are the prominent commands of PuTTYgen in Linux operating system. Besides that, there are many other commands available to perform various tasks from the command prompt in Linux at flank speed.

Types of Keys Supported on PuTTYgen

It is important to know the types of key PuTTYgen supports prior to using it. Below are the key types that it currently supports for SSH-2 and SSH-1 protocol:-