How to convert OpenSSH private key to PuTTY's .ppk

The .ppk format required by PuTTY differs from the default OpenSSH key format commonly used on Linux and other Unix-like systems. OpenSSH relies on PKCS-based standards, while PuTTY uses a separate key representation that must be generated for secure authentication. Understanding these formats ensures seamless transitions between Linux and Windows environments.

The PuTTY Key Generator, commonly referred to as PuTTYGen, performs the necessary conversion by accepting an OpenSSH private key and exporting a fully compatible .ppk file. This approach preserves passphrase protection and cryptographic integrity without requiring multiple keys for different operating systems. It provides a straightforward way to align OpenSSH credentials with PuTTY on Windows.

Using one SSH private key across multiple platforms streamlines user authentication and maintains consistency in both development and production scenarios. Converting existing keys reduces redundant management tasks and simplifies secure remote access. This strategy preserves key integrity and offers a unified workflow in mixed-OS environments.

1. Download PuTTY Key Generator (puttygen.exe) from the official website.

   https://www.chiark.greenend.org.uk/~sgtatham/putty/latest.html

2. Launch PuTTYGen.
3. Click on the Load button.
4. Set the Files of type to All Files (*.*), select your SSH's private key file and click on the Open button.
5. Enter your key's passphrase if prompted and click on the OK button.
6. A prompt will pop up once the conversion is successful, and click the OK button.
7. Edit any key parameters if necessary and click on Save private key.
8. Select the location and filename to save the generated key and click on the Save button.