The iPhone Dev-Team has released an update regarding jailbreaking and saving your SHSH blobs, just prior to the new 3rd gen iPad announcement. With the release of iOS 5.1 over the air, Apple stop will stop signing 5.0.1 SHSH blobs.
- Soon after 5.1 appears on Apple’s public servers (i.e. iTunes starts to offer it), Apple will stop signing 5.0.1 SHSH blobs.
- If you have an iPhone4S, the basic rule above is really the only rule: you cannot restore back to 5.0.1 once the 5.0.1 signing window is closed, no matter what (even if you saved your SHSH blobs).
- If you have an iPad2 with saved 4.x hashes, you can in fact downgrade to that 4.x but you won’t be able to get to 5.0.1 once the 5.0.1 signing window is closed (even if you saved your 5.0.1 SHSH blobs).
- If you have a device earlier than the iPad2, you can downgrade to whatever version you want, as long as you have saved SHSH blobs for that version. You’ll need the assistance of geohot’s limera1n exploit with tools like redsn0w to get into “pwned DFU mode” and bypass the downgrade restriction.
Essentially what this boils down to for iPhone 4S and iPad 2 users is no downgrading to 5.0.1 even if you’ve saved your SHSH blobs. iPad 2 users can still downgrade to 4.x if they have those blobs and any device before the iPad 2 can downgrade to any version of iOS.
In a nutshell: do not update to iOS 5.1 via iTunes!