MySQL Workbench SSH to Google Compute Fails with "Authentication error opening SSH tunnel" - but Putty works

Question

I am trying to connect to MySQL server hosted on google cloud compute server. I believe the issue is not MySQL authentication related, but rather SSH. MySQL workbench seems to be unable to connect on SSH with "Authentication error opening SSH tunnel".

I am able to open a putty SSH connection to the server using the same IP, user and private key on the same computer.

Connection is configured as:

SSH Hostname: [ip of my google cloud server] 
SSH Username: [username used in putty ssh]
SSH Key File: [same ssh-rsa ppk file I use in putty]
MySQL Hostname: 127.0.0.1
MySQL Server Port: 3306 Username: [mysql user that works from putty] 
Password: [mysql password that works from putty]

wb.log:

09:43:57 [INF][ SSH tunnel]: Existing SSH tunnel not found, opening new one
09:43:57 [INF][ SSH tunnel]: Opening SSH tunnel to 104.197.xxx.xxx
09:43:57 [ERR][sshtunnel.py:notify_exception_error:235]: Traceback (most recent call last):
 File "C:\Program Files\MySQL\MySQL Workbench 6.3 CE\sshtunnel.py", line 303, in _connect_ssh
 look_for_keys=has_key, allow_agent=has_key, timeout=SSH_CONNECTION_TIMEOUT)
 File "C:\Program Files\MySQL\MySQL Workbench 6.3 CE/python/site-packages\paramiko\client.py", line 367, in connect
 look_for_keys, gss_auth, gss_kex, gss_deleg_creds, gss_host)
 File "C:\Program Files\MySQL\MySQL Workbench 6.3 CE/python/site-packages\paramiko\client.py", line 584, in _auth
 raise saved_exception
AuthenticationException: Authentication failed.
09:43:58 [ERR][ SSH tunnel]: Authentication error opening SSH tunnel: Authentication error. Please check that your username and password are correct and try again.
Details (Original exception message):
Authentication failed, please check credentials.
Please refer to logs for details
09:43:59 [INF][ WBContext]: Connection to go-xv01 cancelled by user: Tunnel connection cancelled

• mustaccio: Possible duplicate dba.stackexchange.com/questions/3489/…. As suggested in that topic, Putty uses a non-standard key file format; you'll probably need to export your private key as an OpenSSH key and specify that file in the workbench configuration.
• Ted Scheckler: Yes, that is the solution. Using puttygen to export as Open SSH format works. Open SSH keys begin with "-----BEGIN RSA PRIVATE KEY-----". Thank you.

Answer 1

Based on mustaccio's comment, the solution was using puttygen 'Conversions'->'Import Key'... Then 'Conversions'->'Export Open SSH Key' to export the key. Open SSH keys begin with "-----BEGIN RSA PRIVATE KEY-----".