Cydia’s developer Saurik has put up a lengthy but excellent blog post on Apple’s authoritarian and controlling stance over their hardware, their effort to deadlock the iPhone 3GS from being downgraded and Saurik’s service on Cydia that backs up your 3GS ECID to allow future f/w downgrades. Essential reading if you own a 3GS.
Many 3GS users on are now painfully aware that Apple has stopped signing 3.0 requests and, as a result, they can’t downgrade or even restore to OS3.0. A lucky 50,000 owners managed to save their device’s ECID (unique chip IDs) through Cydia in the brief window that this service was offered before the OS3.1 launch.
However, for those outside the lucky few, all is not lost. A hole in 3.1 has been found and an exploit is being worked on. So the chances for a 3.1 jailbreak are good. Saurik has now reopened his ECID backup facility on Cydia for 3.1 users to ensure they will be able to downgrade back to 3.1 in the future.