Jailbreak iPhone 3.1.2 Firmware using BalckRa1n but unfortunately you can not unlock your iPhone, so this guide is useful only if you want iPhone with authorized carrier.

You can follows this guide to jailbreak 3.1.2 firmware on iPhone/iPhone 3G/iPhone 3GS/iPod Touch 2G & 3G.

Note : Don’t update if your iPhone is on 3.0 or 3.0.1 firmware. Also unlocked iPhone 3G and 3GS users should away from this otherwise you will get your iPhone get locked permanently.

Guide to Jailbreak iPhone 3.1.2 Firmware Using BlackRa1n :

1. Download BlackRa1n from here.

2. Download and then install the latest version of iTunes from here.

3. Now connect iPhone to iTunes and upgrade to 3.1.2 firmware. (Download iPhone 3.1.2 Firmware).

4. Once the updation process gets completed, run BlackRa1n and make sure your iPhone is connected.

5. When BlackRa1n opens up, click “make it ra1n”.

6. Your iPhone should go into recovery mode and you will see GeoHat image instead of default recovery image.

8. The jail breaking process will start and your iPhone will reboot automatically.

9. Post reboot, you will see BlackRa1n in the list of applications in your iPhone. Run BlackRa1n and install Cydia.

10. Reboot your iPhone and that all.