Updating 2g iphone
Newer devices like the i Pad 2, i Pad 3, i Phone 4S, i Phone 5 and i Pod Touch 5G has different restrictions however, because they are not vulnerable to the limera1n exploit and are governed more-so by APTickets.These devices can only be downgraded on the i OS 5 firmware generation and require saved SHSH blobs and APTickets for the i OS 5 firmware version you are currently running and are trying to get to.
What is happening is Apple refuses to generate the new hash during the downgrade, meaning the new SHSH blobs cannot be generated.If you are Jailbroken then most of the times your SHSH blobs are already saved on Cydia’s server automatically and you shouldn’t have to back them up manually.Sometimes Cydia doesn’t back up your SHSH blobs on your Jailbroken device however, and you might even prefer to do a local backup of your SHSH blobs.In case this wasn’t a big enough limitation to downgrading i OS devices, in the i OS 5 firmware generation Apple introduced yet another technology to prevent downgrading called APTickets.What APTickets are is essentially the next generation of SHSH blobs.Whenever you upgrade or downgrade your i Phone, i Pod Touch or i Pad, new SHSH blobs have to be generated because one of the parts to the SHSH formula is the firmware version.
In order to prevent firmware restores Apple only signs one firmware version at a time, which is obviously the latest firmware version available.
Note #1: This is not some magical section of guides that will allow you to downgrade your i Phone, i Pod Touch, i Pad or Apple TV 2G without having your SHSH blobs saved for prior firmware versions.
Meaning you had to have saved your SHSH blobs for the firmware version you are trying to downgrade to, or downgrading will not work.
You see, when Apple is still signing a firmware version you can save the SHSH signature so that in the future if you wish to downgrade back to that firmware version it is indeed possible.
This is essentially performing a replay attack, in the fact that data is being fraudulently retransmitted.
In the early days you could downgrade your i OS device to any firmware version you wanted to and not run into many troubles.