Sn0wbreeze lets you create custom IPSW firmware to jailbreak iOS 4.3. This jailbreak however is tethered and requires you to use iBooty to boot your iDevice into jailbroken state. Note that MobileSubstrate is broken on iOS 4.3 which means many Cydia apps including SBSettings will not work.Sn0wbreeze is a Windows only tool. Mac users may want to look at the unofficial PwnageTool Bundles to jailbreak iOS 4.3 on iPhone 4, iPhone 3GS, iPad, iPod Touch 4G, 3G.