I believe i got your point, if correct this could help.
when the Keys is generated by a third party tool or using a Linux Machine, it is created as separate two files one is the public and one is the private...
By default there is no key installed in the switch and we need to manually input the public key to the switch and map it to an existing user, This is by design and could not be changed.
May be if you go though this article on how to create the RSA key and install it in the switch should give you exact idea
So what you are looking for is not an option.