Why "urgently?"

Is your homework due in the morning? Is your probationary period about to end?

Your problem statement also involves multiple questions with little evidence you're expended any effort on any one of them.

So, do a little work toward on your own. See what CPAN might offer; for example, read the documentation for Net::SFTP. Search CPAN for "RSA."

Oh yes, re-read your own post: What you wrote makes this challenge sound like homework -- which we'll help with but NOT do for you
      ...but in such a case, we prefer immediate disclosure by the Seeker.