TinyUmbrella facilitates the process of restoring your iPhone's iOS, and is also useful for jailbreaking the device. It does two things:
- Requests SHSH signatures for firmware restores
- Plays back those signatures enabling iTunes to continue the restore
TinyUmbrella sends the same exact request that iTunes sends Apple when requesting the signatures for your device to be restored. The difference is that TinyUmbrella does not need to do anything to your device. You do not need to be on the firmware version that TinyUmbrella is requesting signatures. As an example, I've been on 3.1.2 for quite some time. TinyUmbrella has saved my 3.1, 3.1.2 and 3.1.3 signatures. This is because the request that iTunes sends to Apple includes your ECID and the details about the firmware version. Apple sends the response signatures and TinyUmbrella saves them so you can use them whenever you want; Even if Apple has stopped signing that particular version.