How to convert PPK key to OpenSSH using PuTTYGen

PuTTY's .ppk key format is not compatible with OpenSSH. To use a .ppk key with OpenSSH, you must first convert it to the OpenSSH private key format.

This conversion can be done easily with PuTTYGen, a tool specifically designed for managing and converting PuTTY keys. It supports exporting a .ppk file to a format recognized by OpenSSH.

Once converted, the key can be used with any OpenSSH client. This ensures compatibility across different systems and platforms.

1. Download PuTTYGen (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 on PuTTYGen's main interface.
4. Select your PuTTY's private key file which normally ends with .ppk extension and click on the Open button.
5. Enter the key's passphrase if prompted and then click OK.
6. Details of the imported key will be displayed on the main interface and edit if necessary.
7. Go to Conversions → Export OpenSSH key from the menu.

   There are an old and new types of SSH key file formats and will be automatically be determined based on the key's type except if you choose Export OpenSSH key (force new file format).

8. Select the location and file name for your OpenSSH private key and click on the Save button.