Attention all losers who updated to 3.1.2 – you’re not completely lost just yet. GeoHot (yes, the guy who seems competely obsessed with himself, even to the point where he puts his face as the bootrom image when jailbreaking your iDevice) has released blackra1n a few days ago.

GeoHot's blackra1n jailbreak running on a iPhone.
What is this “blackra1n” you might ask? It’s a software unlock for the iPod touch and iPhone. iPod touch 3G owners, this is a semi-tethered jailbreak for you guys, so you have to connect it to a PC and run this each time you want to turn your iPod on.) iPhone users, take heed! This isn’t a baseband unlock, it’s software based. More questions are shot this way asking “What’s baseband, exactly?” Consider it an extension on your iPhone, it’s the part that handles the networking aspects of the iPhone. Kinda like a modem, video card, or any other extension that you might need on your computer. It’s a separate piece of hardware living in the iPhone, who’s firmware differs from the iPhone OS’s firmware.
“Why do I give a damn?” Because if you’ve already upgraded via iTunes to 3.1+, your baseband also got upgraded, and as of now, there’s no way to perform a carrier unlock. So if you were dependent on a carrier unlock to use your phone, and for some reason upgraded, you’re screwed, and you deserve to be.
For those who actually use the carrier your iPhone was intended to be used by (AT&T over here in the states), this doesn’t really matter now does it? So let’s continue on to how to use this unlock.
If you remember a while back, this same GeoHot guy also released purplera1n, an unlock for the iPhone 3G S, when the iPhone Dev-Team was still working on one to upgrade their redsn0w program with. It all came as a surprise really, but man were us hackers pumped… My new iPhone 3G S could now have the joy and open-ness of a jailbroken iPhone, and that’s where it’s at right now, 3.0, jailbroken, with a carrier patch to get MMS. Customized just the way I like it, mobilesubstrate extensions, all my custom apps, and my lovely springboard theme.
Okay, now let’s get down to business… remember, if you’re not on a Apple approved carrier, then blackra1n won’t be able to activate your iPhone. iPod touch users, go ahead with no worries, you don’t even have a baseband that you need to worry about. For a summary of the whole “baseband” thing, here’s a quote from iClarified.
“WARNING: Even though the GeoHot jailbreak supports 3.1.2 do not update if you are on iPhone OS 3.0.1 or 3.0. You will lose your unlock. Use PwnageTool to safely update to 3.1 without performing a baseband update. If you really must have 3.1.2 then wait for the next version of PwnageTool. If you have already updated to 3.1 or 3.1.2 without using PwnageTool then you’ve lost the ability to unlock for the time being. You can now use BlackRa1n to at least regain your jailbreak
”
So let’s get on to that jailbreak, finally. Download blackra1n from blackra1n.com. Click on the Windows logo at the bottom to download the .exe. Once you’re done with the download, open the program.

It’s now safe to connect your iPhone / iPod touch, gather some dignity and click the giant “make it ra1n” button. If you can’t seem to find it, go jump off a cliff.
Click it, and BAM, there’s the conceited bastard himself, right on your iDevice. Okay, once your iDevice boots to the home screen, there’s a nifty new app called “blackra1n” somewhere on there. Open it, you now have a choice between Cydia, Rock, and Icy. Icy and Cydia are two of the the apps I’m used to, I’ve never used Rock, so if I were you, I’d go with the original and more popular choice, Cydia. You can install all if you’d like though. With your cellular or WiFi network, blackra1n will begin to download and install the application(s) you chose.

Once this is done, you’ll have Cydia (or some other installer) located on your homescreen. You can now use this program to install further hacks and enhancements. Congratulations, you’re on a jailbroken iPhone / iPod touch. Enjoy, and try to resist downloading iSteamy.
If you have any problems, @reply / DM me on Twitter, @AdeptHavok. I’ll help ya. Pinkie promise.
UPDATE: A Mac version of this exploit is now avaliable on the blackra1n website.