So I asked a similar question on the iBook form, and even though I don't plan to use my Late 2001 iBook a lot, what is the first version of OS X that supports Wi-Fi securities WPA/WPA2.
iBook, Mac OS X (10.1.x), Late 2001, 500MHz, OS 9 Installed
10.3.3 and higher support WPA2 network security protocols
However, WPA2 is as much a function of Hardware as software. No iBook G3 supports WPA2 through the original airport card. Some third party cards have been successfully hacked to support 802.11g but not with Apple's drivers. USB WPA2 compatible cards are limited to USB 1.1 's 15 Mbps, and ethernet WiFi bridges with WPA2 get the full 33 Mbps of 802.11g. Uncertain if any of those bridges will go up to the 100 Mbps of the ethernet if you have an 802.11n bridge, but you could try if you need both the speed and the security.
What is the First Version of OS X
