Which two configurations are necessary to enable password-less SSH login to an IOS router?

Which two configurations are necessary to enable password-less SSH login to an IOS router?
(Choose two.)

A.
Enter a copy of the administrator’s public key within the SSH key-chain

B.
Enter a copy of the administrator’s private key within the SSH key-chain

C.
Generate a 512-bit RSA key to enable SSH on the router

D.
Generate an RSA key of at least 768 bits to enable SSH on the router

E.
Generate a 512-bit ECDSA key to enable SSH on the router

F.
Generate a ECDSA key of at least 768 bits to enable SSH on the router