I'm one of the few people apparently still rocking the iPhone 4, so this doesn't apply to me and I have no way of testing it, but I have a number of friends who've been complaining that iOS 8 has made their iDevices sluggish and buggy (especially the 4s and iPad 2/3). I found it weird that there was absolutely no way to get around the firmware signing requirements... until I stumbled across this: http://www.saurik.com/id/12
"To this end, I have constructed a server that duplicates the functionality exposed by Apple's signature server, except using "on file" results rather than live requests.
All we need, then, is to make iTunes use it. Luckily, most operating systems also have the ability to locally define bypasses on specific hostnames through a file called hosts. Using this, we can redirect requests to Apple's signature server to Cydia.
So, open the file C:\Windows\System32\drivers\etc\hosts (Windows) or /etc/hosts (Mac OS X) and add the following entry to the bottom of the file.
74.208.10.249 gs.apple.com
Now, when iTunes thinks it is talking to Apple, it is talking to Cydia instead. Doing this will allow iTunes to access signatures already stored by Cydia's "on file" feature.
This server will also act as a cache for any SHSH blobs it hasn't seen, acting as an intermediary to Apple's server. This effectively registers your device with the "on file" mechanism, which means you can now enjoy the protections of being able to downgrade your firmware in the future even if you aren't jailbroken."
I have no way of testing this myself, and your mileage may vary, but from what I can see, it looks like it should work and allow you to downgrade your firmware (to any version, for that matter, not just 7.1.2). I'd love for someone to let me know if it works! Proceed with caution, obviously.
Anyway, hopefully some of you find this useful.
"To this end, I have constructed a server that duplicates the functionality exposed by Apple's signature server, except using "on file" results rather than live requests.
All we need, then, is to make iTunes use it. Luckily, most operating systems also have the ability to locally define bypasses on specific hostnames through a file called hosts. Using this, we can redirect requests to Apple's signature server to Cydia.
So, open the file C:\Windows\System32\drivers\etc\hosts (Windows) or /etc/hosts (Mac OS X) and add the following entry to the bottom of the file.
74.208.10.249 gs.apple.com
Now, when iTunes thinks it is talking to Apple, it is talking to Cydia instead. Doing this will allow iTunes to access signatures already stored by Cydia's "on file" feature.
This server will also act as a cache for any SHSH blobs it hasn't seen, acting as an intermediary to Apple's server. This effectively registers your device with the "on file" mechanism, which means you can now enjoy the protections of being able to downgrade your firmware in the future even if you aren't jailbroken."
I have no way of testing this myself, and your mileage may vary, but from what I can see, it looks like it should work and allow you to downgrade your firmware (to any version, for that matter, not just 7.1.2). I'd love for someone to let me know if it works! Proceed with caution, obviously.
Anyway, hopefully some of you find this useful.