How to convert a PPK key to RSA

Putty is a common windows SFTP and SSH client that uses a different key format to most other tools. Its fairly common to need to convert keys between formats.

Converting using Putty

1. Install PuTTYgen

• If you don’t already have it, download PuTTYgen from the PuTTY download page.

• On Windows, it usually installs along with PuTTY.

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2. Open Your PPK File

1. Launch PuTTYgen.

2. Click Load and browse to your .ppk file.

   • You might need to set the file filter to *.* to see your PPK.

3. Once loaded, you’ll see details about the key.

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3. Export the PEM Key

1. From the Conversions menu, choose:

   • Export OpenSSH key → creates a PEM suitable for SSH.

   • Export OpenSSH key (force new file format) → for newer OpenSSH versions.

   • Export OpenSSH key (old PEM format) → if something expects “classic” PEM.

2. Save the file with a .pem extension (e.g., mykey.pem).

Using the command line

If you have a PPK file on Linux or macOS, you can also use puttygen (installed via package manager):

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

• -O private-openssh → outputs an OpenSSH-compatible PEM private key.

• -o mykey.pem → specifies the output filename.

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After this, you can use the .pem file with OpenSSH or cloud providers like AWS EC2.