[update]Redsn0w 0.9.11b2 can now downgrade iPad2/3 and 4S

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5x redux

What’s old is new again!
Jailbreakers
with devices that pre-date the iPad2 will always be able to downgrade
(with SHSH blobs) to previous firmware versions due to geohot’s
limera1n exploit, which allows us to bypass the restrictions that Apple
places on restores. But until now, that ability has been limited to
those older devices (if you have an older device and don’t know how to
do that, check the popular tutorial sites or ask in the comments
below).

Starting with redsn0w version 0.9.11b1, those with newer devices (iPad2,
iPad3, and iPhone4S) can join the downgrade fun too! In a radical
departure from previous versions of redsn0w, it now directly supports
restoring IPSWs to your device. The first use of this new feature
implements a hack that allows A5 downgrades without a bootrom-level
exploit.

Some important points:

You
cannot downgrade without the personalized SHSH blobs for your device
at that lower firmware. You need to have fetched those blobs while the
signing window was open, using either Cydia’s built-in TSS@Home
feature, or with TinyUmbrella. The new Restore screen of redsn0w lets
you choose either the remote blobs or local ones (for the earlier
firmware). If you don’t know where TinyUmbrella put your blobs,
TinyUmbrella has a button that will show you (copy them out of that
folder and feed them to redsn0w).
The A5 downgrade method
actually updates to the latest firmware before downgrading to the
earlier one. This process updates your baseband to whatever is newest.
DO NOT USE THIS METHOD IF YOU RELY ON UNOFFICIAL UNLOCKS of your
iPhone4S. Those who used the temporary SAM technique to unlock their
iPhones to specific SIMs shouldn’t be affected by this baseband update.

This method can be fixed by Apple with a firmware update. It’s a
(pleasant) mystery why they haven’t fixed it yet, because
reverse-engineering of the restore ramdisk indicates they do know about
it. It’s possibly too niche to bother to fix right now.

The least-tested devices with this method are the iPad2,3 and iPad3,2
(because we don’t have those models). If you do and you feel like
experimenting, please let us know how it turns out in the comment
section below!
This update involves a bunch of new redsn0w
code. We recommend sticking to the previous version 0.9.10b8b unless
you’re specifically using this new feature, until all the bugs are
worked out! (Note: If redsn0w gets stuck at the “Waiting for device”
stage for more than 30 seconds, you’ve hit a pesky GUI bug…that will be
fixed in an upcoming version!)

Of course all eyes are on @pod2g for his upcoming 5.1 untethered jailbreak. Watch his [You must be registered and logged in to see this link.]
or twitter feed for the latest updates about that, but in the meantime
if you accidentally updated your jailbroken A5 device to something
later than 5.0.1, feel free to try this new A5 firmware downgrade
feature of redsn0w!

Update #1: We
accidentally left out one of the two flavors (“9A406”) of 5.0.1 for
iPhone4S. It’ll be in the next update, but in the meantime check if
Cydia or TU saved your blobs for the other 5.0.1 for iPhone4S
(“9A405”). Version 0.9.11b2 adds support for that second “9A406” flavor of 5.0.1 for the iPhone4S

Here are the redns0w download links:

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