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Changes to Apple's TSS servers currently render Prometheus non functional
Hot on the heels of Prometheus' release at the 33c3 convention two days ago, tihmstar's tool for upgrading and downgrading to unsigned iOS firmwares seems already to have hit a snag. Following some changes to Apple's TSS servers today, the nature of which are yet to be investigated, the tool has been rendered non-functional at the present time.The first misconception to clear up, which has been repeated in many places, is that Apple has completely taken its TSS servers offline. That is not the case; the servers are clearly still up, as can be proven by attempting to restore or upgrade a device through iTunes. If the TSS servers truly were down, no iTunes restores would be able to complete.Having said that, some changes to the servers do seem to have been made, as attempting to connect to them returns an error, and Prometheus is unable to proceed at the present time. This is due to the fact that it relies on currently signed SEP and baseband sections during its restore process. Even though it circumvents signing for the rest of the process by using your saved blobs, an inability to get the TSS server to approve the SEP and baseband signing will cause the tool to fail.A second rumour which has been perpetrated by some is that Apple will temporarily sign all firmwares when the servers come back online. Whilst this is not literally impossible, it is almost certainly false. Firstly, because as already discussed the servers are not totally down, and secondly, because there is no reason to think they would be forced to do so even if they were. This idea seems to be driven more by hope than anything else, and I would not place any amount of reliance in it, especially not in making decisions about upgrading or downgrading your devices.