Hi Vishnu
This finding confirms that the error that you are facing is due to unlimited JCE was not installed on your QA system. The error is the expected behaviour in such a case, and not because of SFTP key issues.
For next steps, please follow the link provided in my first response to this thread for the steps on how to install unlimited JCE.
Btw, if your Dev system already has unlimited JCE, this would mean someone (probably from Basis team) already performed the installation and would be aware of the steps.
Make sure also that this installation is done in other systems in your landscape (Prod, etc).
Rgds
Eng Swee
