Putty new vesion of PPK file

[rehanvdm]

The 2021-04-18 release of putty introduced version 3 PuTTY-User-Key-File-3 of the PPK file. If you have an old version of putty then it can not use the new version.

Release notese here: https://www.chiark.greenend.org.uk/~sgtatham/putty/

2021-04-18 Pre-releases of 0.75 now available We've introduced a new version of the PPK format for private key files, to remove weak crypto and improve password-guessing resistance.

More info on what changed https://tartarus.org/~simon/putty-prerel-snapshots/htmldoc/AppendixC.html#ppk-old between the versions.

This means the privateKeyToPutty would now need to accept another input to specify the version number as it is currently generating version 2 and not 3.

forge.ssh.privateKeyToPutty(privateKey, passphrase, comment);