Tested and corrected via these instructions: https://askubuntu.com/questions/46930/how-can-i-set-up-password-less-ssh-login
The instructions here worked flawlessly when I tested on my boxes (CentOS/CentOS). I imagine the issue is your ssh keys are not tied to a username.
Example: cat authorized_keys # on Box I'm sshing/scpin' to ssh-rsa BLAHBLAHBLAHBLAH/zAcS4kD9pyPAjD3/gd5D1rcQa6IztCMR9yMXiGFnxviWsT8/oYevZw25k4yREuA8ibLKC9peH1X4LK1E+n7gq4TETexWkZbQ2XGLOX44eglra3MB4FShPg0cZXGcJWltPQ/y0Ay2A/KmaC14YrDfqwm7+ibTiUp4hOO8I6eIPmwwGn/2hs0SewJXisGqUx2v my_user@machine.local #username is tied to the key and is an authorized host