I don't know much about encryption key, but I do know how to move files around and change permission.
$mv /current/path_to/foo.key /www/user/public_html/
$chown nobody.nobody foo.key (change file/dir to be owned by user nobody and group nobody)
$chmod 750 foo.key (this will make sure the file is accessible by the webserver but denied to anyone else)
Ask around about webserver and encryption key.