PuTTY stores keys in its own format in .ppk files.
PUTTYGEN - KEY GENERATOR FOR PUTTY ON WINDOWS
- Start menu → All Programs → PuTTY→ PuTTYgen.
- Click Generate, and start moving the mouse within the Window. Putty uses mouse movements to collect randomness. As you move it, the green progress bar should advance.
- Specify a passphrase for the key if keys are NOT needed for automation (e.g., with WinSCP)
- Save private key.
- Save the public key (It can be later regenerated by loading the private key by clicking Load).
then see : Key usage
Documentation / Reference
- The authors of PuTTY claim that it is the best one