TortoiseHG relies on the PuTTYgen utility to generate an identity. If you are following along in this tutorial, you should have already installed PuTTYgen. If you used PuTTYgen in the past to generate an identity, you should have an identity.ppk file on your system. If you have an existing private key, you can skip Step 2 below and go onto Enable SSH compression for Mercurial. Otherwise, continue to the next step.