github ssh:
https://help.github.com/articles/generating-ssh-keys/
https://help.github.com/articles/working-with-ssh-key-passphrases/
http://superuser.com/questions/441854/git-ssh-agent-not-working

https://wiki.archlinux.org/index.php/SSH_keys
ssh-keygen -t rsa -b 4096 -C "your_email@example.com" -f <some-file>
    will generate <some-file> with a pvt-key and <some-file>.pub with a pub-key
ssh-copy-id <user>@<host>
-> ~/.ssh/authorized_keys
ssh-copy-id -i ~/.ssh/id_rsa.pub user@host

PVT KEYS:
sudo chmod 0500 ~/.shh/id_rsa

Multiple keys:
http://stackoverflow.com/questions/10455974/setting-up-ssh-keys-for-gibhub

Password-protect key:
https://help.github.com/articles/working-with-ssh-key-passphrases/
ssh-keygen -p -f /path-to/key-file