Blackra1n claims to be a 30-second jailbreaking tool for all devices running the iPhone 3.1.2 firmware. I didn’t have much success when I ran the app, but a lot of people seem to be having more luck than I.
The Blackra1n blog warns that 3G or 3GS users who require their phones to be unlocked should not upgrade to 3.1.2 just yet as their phones will no longer be unlocked, pretty much transforming their devices into an iPod Touch. Blackra1n also does not hacktivate your device.
well blackra1n work great on the 3.1.2 . in my case i was using 3.1 and after i install thewinter board the iphone was powering un and the shut down.