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. Convert Pem to Ppk File Using PuTTYgen. PuTTYgen, part of the open source network networking client PuTTY, is a crucial generating tool to create public and private SSH keys for servers. The native file format of PuTTY is.ppk files. Additionally, the tool is used for SSH connectivity. How to convert SSH key to PuTTY's.ppk SSH and PuTTY keys are of different formats and will have to be converted to each other's format if you want to use the same key between the 2 programs. Follow these steps to convert SSH 's key to PuTTY 's. For a number of our services, we ask you to provide a private SSH key. For PuTTY users, this can cause an issue as we do not use the PuTTY-keygen format. Here is how you can convert your PuTTY key to OpenSSH format: Open your private key in PuTTYGen Top menu “Conversions”-”Export OpenSSH key”. Save the new OpenSSH key when prompted. OpenSSH is the de facto standard implementation of the SSH protocol. If PuTTY and OpenSSH differ, PuTTY is the one that's incompatible. If you generate a key with OpenSSH using ssh-keygen with the default options, it will work with virtually every server out there.
PuTTYgen is a key generator. It generates pairs of public and private keys to be used with WinSCP. PuTTYgen generates RSA, DSA, ECDSA, and Ed25519 keys.
PuTTYgen is included in the WinSCP installation package. You can also download it separately from the WinSCP download page.
PuTTYgen originates from PuTTY and is also part of the PuTTY installation package. It does not matter if you use PuTTYgen from WinSCP or the PuTTY installation package, they are identical.
To start PuTTYgen, go to Tools > PuTTYgen on Login dialog.
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When you run PuTTYgen you will see a window where you have two main choices: Generate, to generate a new public/private key pair, or Load to load in an existing private key.
This is a general outline of the procedure for generating a new key pair. The following sections describe the process in more detail.
Your key pair is now ready for use. You may also want to copy the public key to your server, either by copying it out of the Public key for pasting into OpenSSH authorized_keys file box, or by using the Save public key button. However, you don’t need to do this immediately; if you want, you can load the private key back into PuTTYgen later and the public key will be available for copying and pasting again.
For more details refer to guide to setting up public key authentication.
Before generating a key pair using PuTTYgen, you need to select which type of key you need.
The current version of the SSH protocol, SSH-2, supports several different key types. PuTTYgen can generate:
PuTTYgen can also generate an RSA key suitable for use with the old SSH-1 protocol (which only supports RSA); for this, you need to select the SSH-1 (RSA) option. Since the SSH-1 protocol is no longer considered secure, it’s rare to need this option.
The Number of bits input box allows you to choose the strength of the key PuTTYgen will generate.
For RSA, 2048 bits should currently be sufficient for most purposes.
For ECDSA, only 256, 384, and 521 bits are supported. (ECDSA offers equivalent security to RSA with smaller key sizes.)
For Ed25519, the only valid size is 256 bits.
Once you have chosen the type of key you want, and the strength of the key, press the Generate button and PuTTYgen will begin the process of actually generating the key.
First, a progress bar will appear and PuTTYgen will ask you to move the mouse around to generate randomness. Wave the mouse in circles over the blank area in the PuTTYgen window, and the progress bar will gradually fill up as PuTTYgen collects enough randomness. You don’t need to wave the mouse in particularly imaginative patterns (although it can’t hurt); PuTTYgen will collect enough randomness just from the fine detail of exactly how far the mouse has moved each time Windows samples its position.
When the progress bar reaches the end, PuTTYgen will begin creating the key. The progress bar will reset to the start, and gradually move up again to track the progress of the key generation. It will not move evenly, and may occasionally slow down to a stop; this is unfortunately unavoidable, because key generation is a random process and it is impossible to reliably predict how long it will take.
When the key generation is complete, a new set of controls will appear in the window to indicate this.
The Key fingerprint box shows you a fingerprint value for the generated key. This is derived cryptographically from the public key value, so it doesn’t need to be kept secret; it is supposed to be more manageable for human beings than the public key itself.
The fingerprint value is intended to be cryptographically secure, in the sense that it is computationally infeasible for someone to invent a second key with the same fingerprint, or to find a key with a particular fingerprint.
If you have more than one key and use them for different purposes, you don’t need to memorize the key fingerprints in order to tell them apart. PuTTYgen allows you to enter a comment for your key, which will be displayed whenever WinSCP or Pageant asks you for the passphrase.
The default comment format, if you don’t specify one, contains the key type and the date of generation, such as rsa-key-20011212. Another commonly used approach is to use your name and the name of the computer the key will be used on, such as simon@simons-pc.
To alter the key comment, just type your comment text into the Key comment box before saving the private key. If you want to change the comment later, you can load the private key back into PuTTYgen, change the comment, and save it again.
The Key passphrase and Confirm passphrase boxes allow you to choose a passphrase for your key. The passphrase will be used to encrypt the key on disk, so you will not be able to use the key without first entering the passphrase.
When you save the key, PuTTYgen will check that the Key passphrase and Confirm passphrase boxes both contain exactly the same passphrase, and will refuse to save the key otherwise.
If you leave the passphrase fields blank, the key will be saved unencrypted. You should not do this without good reason; if you do, your private key file on disk will be all an attacker needs to gain access to any machine configured to accept that key. If you want to be able to passwordless log in without having to type a passphrase every time, you should consider using Pageant so that your decrypted key is only held in memory rather than on disk.
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Under special circumstances you may genuinely need to use a key with no passphrase; for example, if you need to run an automated batch script that needs to make an SSH connection, you can’t be there to type the passphrase. In this case we recommend you generate a special key for each specific batch script (or whatever) that needs one, and on the server side you should arrange that each key is restricted so that it can only be used for that specific purpose. The documentation for your SSH server should explain how to do this (it will probably vary between servers).
Choosing a good passphrase is difficult. Just as you shouldn’t use a dictionary word as a password because it’s easy for an attacker to run through a whole dictionary, you should not use a song lyric, quotation or other well-known sentence as a passphrase. If you want your passphrase to make grammatical sense, this cuts down the possibilities a lot and you should use a longer one as a result.
Do not forget your passphrase. There is no way to recover it.
Once you have generated a key, set a comment field and set a passphrase, you are ready to save your private key to disk.
Press the Save private key button. PuTTYgen will put up a dialog box asking you where to save the file. Select a directory, type in a file name, and press Save.
This file is in PuTTY’s native format (*.PPK
); it is the one you will need to tell WinSCP to use for authentication.
If you have started PuTTYgen from SSH > Authentication page of Advanced Site Settings dialog, WinSCP automatically detects the saved key and will insert its path it into Private key file box.
RFC 4716 specifies a standard format for storing SSH-2 public keys on disk. Some SSH servers (such as ssh.com’s) require a public key in this format in order to accept authentication with the corresponding private key. (Others, such as OpenSSH, use a different format)
To save your public key in the SSH-2 standard format, press the Save public key button in PuTTYgen. PuTTYgen will put up a dialog box asking you where to save the file. Select a directory, type in a file name, and press Save.
You will then probably want to copy the public key file to your SSH server machine.
If you use this option with an SSH-1 key, the file PuTTYgen saves will contain exactly the same text that appears in the Public key for pasting box. This is the only existing standard for SSH-1 public keys.
The OpenSSH server, among others, requires your public key to be given to it in a one-line format before it will accept authentication with your private key. (SSH-1 servers also used this method.)
The Public key for pasting into OpenSSH authorized_keys file gives the public-key data in the correct one-line format.
For more details refer to guide to setting up public key authentication.
WinSCP can show you the public key too.
PuTTYgen allows you to load an existing private key file into memory. If you do this, you can then change the passphrase and comment before saving it again; you can also make extra copies of the public key.
To load an existing key, press the Load button. PuTTYgen will display a dialog box where you can browse around the file system and find your key file. Once you select the file, PuTTYgen will ask you for a passphrase (if necessary) and will then display the key details in the same way as if it had just generated the key.
If you use the Load command to load a foreign key format, it will work, but you will see a message box warning you that the key you have loaded is not a PuTTY native key. See below for information about importing foreign key formats.
SSH-2 private keys have no standard format. OpenSSH and ssh.com have different formats, and WinSCP’s is different again. So a key generated with one client cannot immediately be used with another.
Using the Import command from the Conversions menu, PuTTYgen can load SSH-2 private keys in OpenSSH’s format and ssh.com’s format. Once you have loaded one of these key types, you can then save it back out as a PuTTY-format key (*.PPK
) so that you can use it with the WinSCP. The passphrase will be unchanged by this process (unless you deliberately change it). You may want to change the key comment before you save the key, since some OpenSSH key formats contained no space for a comment, and ssh.com’s default comment format is long and verbose.
PuTTYgen can also export private keys in OpenSSH format and in ssh.com format. To do so, select one of the Export options from the Conversions menu. Exporting a key works exactly like saving it – you need to have typed your passphrase in beforehand, and you will be warned if you are about to save a key without a passphrase.
For OpenSSH there are two options. Modern OpenSSH actually has two formats it uses for storing private keys. Export OpenSSH key will automatically choose the oldest format supported for the key type, for maximum backward compatibility with older versions of OpenSSH; for newer key types like Ed25519, it will use the newer format as that is the only legal option. If you have some specific reason for wanting to use OpenSSH’s newer format even for RSA, DSA, or ECDSA keys, you can choose Export OpenSSH key (force new file format).
Most clients for the older SSH-1 protocol use a standard format for storing private keys on disk. PuTTY uses this format as well; so if you have generated an SSH-1 private key using OpenSSH or ssh.com’s client, you can use it with WinSCP, and vice versa. Hence, the export options are not available if you have generated an SSH-1 key.1
You can also use WinSCP /keygen
command-line switch to convert the private key from other formats.
PuTTYgen is a key generator tool for creating pairs of public and private SSH keys. It is one of the components of the open-source networking client PuTTY. Although originally written for Microsoft Windows operating system, it is now officially available for multiple operating systems including macOS, Linux. PuTTYgen.exe is the graphical tool on Windows OS. While on the other side, Linux OS has the only command-line version could be accessible using SSH commands.
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.
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:
Various Ways to Use RSA Key Pair
RSA key pair generated through PuTTYgen is used in two various ways defined as below:
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.
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.
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:
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.
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.
Mac has the port of PuTTY which can be installed in various ways described as below:
sudo brew install putty
sudo port install putty
–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.
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
To create the key pair for authentication in Linux use the below command:-
puttygen -t rsa -b 2048 -C 'user@host' -o keyfile.ppk
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:
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.
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:-
The above description is a detailed brief on downloading and running PuTTYgen on all major operating systems. For further details please check the Download PuTTY page.