Since George Hotz (a.k.a GeoHot) showed an untethered boot of an iPod touch 3G a few days ago, it’s even more important then it already was, to grab your 3.1.2 or 3.1.3 SHSH on file. Because this exploit is an iBoot exploit which can be fixed by Apple in a firmware revision. With your ECID SHSH on file, you will be able to always downgrade to that lovely bugged iBoot and untether jailbreak your device. Apple released firmware 3.2 for iPad and iPhone update is also just around the corner, so it is highly recommended to save your SHSH, if you really care about your jailbreak.
In this quick explanation we’ll talk about what to do when you’re jailbroken and what especially what to do when you are not.
I am already Jailbroken
A lot of you who are jailbroken have chosen for the "make my life easier" option that Cydia offered back in September. That was the best thing you did in the war against the ECID checks by Apple. Cydia backed up your ECID SHSH’s on file and are now stored in saurik’s server. When you put the address of saurik’s server in the hosts file of your OS, you will always be able to downgrade to the earlier firmware versions (or a buggy iBoot) that Cydia created SHSH’s on file for. So in that situation, you’re covered and well.
I just bought an iPhone 3.1.3 and it’s not jailbroken
Say that you’re a bit afraid of jailbreaking and you just want to see how it all goes in the scene, but you want to make sure that you will be able to jailbreak in the future. Well then it’s also very, very important that you grab your ECID SHSH as soon as possible. When Apple stops signing 3.1.3 and patches holes (which will probably only be revealed when iPhone OS 4.0 drops out), you won’t be able to jailbreak anymore until another exploit is found and revealed. And since the iPhone Dev‐Team is very distant with exploits, it will probably be not be anytime soon. Anyway, you can grab your ECID SHSH on file even when you are not jailbroken, and here is how to do it Getting 3.1.3 SHSH Signature Files for Your iPhone
Of course this will only be possible for the firmware version Apple still signs, which is (right now) 3.1.3. NOTE: it is very important to keep doing this for every firmware version that comes out after these!!