How To Generate Putty Keys wit Puttygen?

Puttygen is used to generate ssh public and private keys for putty. We can use a different type of encryption algorithm bit sizes and ssh versions. In this tutorial, we will look at useful examples of puttygen.

Install Puttygen To Linux

puttygen is provided with putty packages most of the Linux distributions like Ubuntu, Debian, Fedora, CentOS, RedHat.

Ubuntu, Debian

puttygen tool is provided with the putty package in Debian, Mint, Ubuntu, Kali.

$ sudo apt install putty

Fedora, CentOS, RedHat

puttygen tool is provided with the putty package in Fedora, CentOS, RedHat.

$ sudo yum install putty

Windows

Windows binaries are provided with the following URL.

32 bit

https://the.earth.li/~sgtatham/putty/latest/w32/puttygen.exe

64 bit

https://the.earth.li/~sgtatham/putty/latest/w64/puttygen.exe

puttygen Command Syntax

The syntax of puttygen is like below. puttygen is a simple command where there are two parameters named KEYFILE, OPTIONS.

puttygen KEYFILE OPTINONS

KEYFILE is the file we read
OPTIONS are used to specify size, output key file, etc.

Create Key From puttygen GUI

puttygen tool is provided with a GUI in Windows operating systems. We can download this GUI tool which is explained in the Download For Windows section. Then from the tool, we will be provided a simple screen where we can set different parameters about the cryptographic key creation.

We can see that there is 3 main part of the window.

Key part provides the key in ASCII format.
Actions part will provide buttons for Key generation, Load Existing Key, Save Public Key, Save Private Key.
Parameters part provides the key type selection like RSA, DSA, ECDSA, ED25519, SSH-1 (RSA), and the size of the key as bits where default size is 2048 which is accepted as secure.

LEARN MORE How To Solve ssh-copy-id "ERROR: failed to open ID file" Error

Create 2048 RSA Key with Puttygen GUI

We can generate an RSA key which is 2048 bit by using the following configuration for the puttygen. We will click on the Generate button with the default parameters. As cryptography and security are based randomness puttygen need real random data that can be provided with the random mouse hovering over the screen.

At the end of the key generation, the following screen will appear where information about the generated key will be presented.

Key fingerprint is a value that uniquely identifies the created key.
Key comment is a short description of the created key.
Key passphrase is a passphrase or password to encrypt the created key.

We can also create different types and sizes of the keys by changing parameters like below.

Create 2048 DSA Key with Puttygen GUI
Create 4096 RSA Key with Puttygen GUI
Create 4096 DSA Key with Puttygen GUI

Load Existing Key To Puttygen GUI

We can load existing puttygen generated key or key pairs easily. We will use the Load button where we can specify the key file.

Save Generated Public Key To A File

After creating a Public and Private Key Pair we can save these created keys. We can save generated Public Key into a file with the Save public key.

Save Generated Private Key To A File

We can also save the generated Private Key into the file with the Save private key button like below.

Create Key with Default Options From Command Line

We can generate keys with the following command. In this example, we will generate an RSA type key file named test.ppk . ppk is the extension of the putty keys.

$ puttygen -t rsa -o test.ppk

Set Key Size From Command Line

We have the option to set the size of the putty key. More in size means more secure but less performance. But the performance loss is negligible. We can set the size with -b option. We will provide size as a bit unit. In this example, we will set the key file size 4096 bit .

$ puttygen -t rsa -b 4096 -o test.ppk

Change Passphrase From Command Line

Keys are protected with symmetric encryption. This means ppk keys are encrypted and we need to use a passphrase. We can also change the current passphrase with -P option. In order to change the existing passphrase, we should provide old passphrases too.

$ puttygen mykey.ppk -P

Set Comment To Key From Command Line

In the enterprise environment, we may have multiple keys where we cannot remember actually what it was. Or we may need to put some comment about keys on the key file. We can use –C and the comment we want to set.

$ puttygen mykey.ppk -C "My key"