I'm sure you wouldn't steal Cisco software, would you?
To remain legal, you must buy the (re-)license for your equipment.
Part number you want is LL25C=
List price from the pricing tool is CAD$1416 for the IP feature set.
If you already own a legitimate license, the part number you need for an upgrade to IPSec56 would be FL25-L= (CAD$236).
You may need to upgrade to 16D/16F; memoryx.net is a good place for 3rd-party memory.
Good luck.