There's a couple of raffles on here every few days for free keys, and you can buy some CD Keys here(DayZ Selling/Trading/Buying section, where this post probably belongs) for as cheap as $1.50(maybe cheaper than that). I doubt anyone that has excess keys can't hack themselves, so.
But good luck and all that.
Your best bet would be to enter in the raffles posted bellow.
You could try asking someone else who has a lot via PM. But chances are low.
/Closed