ip ssh password-authentication

After the SSH server on the device negotiates a session key and encryption method with the connecting client, user authentication takes place. The implementation of SSH supports DSA or RSA challenge-response authentication and password authentication. You can deactivate one or both user authentication methods for SSH. Note that deactivating both authentication methods disables the SSH server entirely.

With password authentication, users are prompted for a password when they attempt to log in to the device (provided empty password logins are not allowed). If there is no user account that matches the username and password supplied by the user, the user is not granted access.

The no form of the command disables password authentication.