Putty is an SSH client that’s mostly used in Windows. Centos has an SSH client built in. Putty uses its own key format which is not compatible with OpenSSH’s key format. I will show you how to easily convert Putty’s format (mykey.ppk) to OpenSSH’s format (id_rsa) and conversely.
First of all lets install puppy on our Cenos system
# yum install putty
Convert PPK to id_rsa
We have youtube_id_dsa.ppk and need to convert it into openssh format:
# puttygen youtube_id_dsa.ppk -O private-openssh -o id_rsa
This takes youtube_id_dsa.ppk file and converts it to a OpenSSH private key as id_rsa
Convert id_rsa to PPK
# puttygen id_rsa -O private -o private.ppk
This command takes id_rsa file and converts it to a Putty private key format as private.ppk
That's all 