Apple has discontinued support for Phone 2G/ 3G and iPod Touch 1G/2G after the launch of iOS 4.0.However, WhiteD00r project has taken the initiative to help these old devices by porting iOS 4.X on them.
The WhiteD00r project was started in July 2010 with an aim to provide iOS 4.X to these old idevices.
WhiteD00r iOS 4.3 is based on iOS 3 code and it is faster than the iOS4 based one.However,iOS4 based firmware is yet to be released.After upgrading to the latest firmware you will be unable to install iOS4+ only apps from AppStore.
To use WhiteD00r iOS 4.3 you don’t need Apple original firmwares.You will have to download firmware in Zip format which contains a ipsw which you will have to install.It is advisable to use Chrome browser for downloading the firmware.
WhiteD00r has plans to release iOS 4.3 lite version soon.