After upgrading to OS X El Capitan and corresponding upgrade of MacPorts I faced a problem of ssh connection using a public key. While debugging:
$ ssh -v hostname
I have got:
debug1: Skipping ssh-dss key /Users/<user>/.ssh/id_dsa for not in PubkeyAcceptedKeyTypes
The fix was to add to ~/.ssh/config the following string:
PubkeyAcceptedKeyTypes ssh-css
However it was a good trigger to evaluate RSA vs. DSA usage for SSH authentication keys. A good topic for discussion ...