When iTunes verifies the firmware restore for the devices listed below, it checks if you are allowed to restore to the version you are requesting. TinyTSS is a small java app that acts as your very own signature service. It saves SHSH signatures for your device received from the Apple server and let to downgrade OS indefinitely. Apple stops signing older firmwares once a new one is out.įirmwareUmbrella sends the same exact request that iTunes sends Apple when requesting the signatures for your device to be restored. If the signature does not match, the device raises an error and the restore process stops. If the signature matches then the restore process can continue. Your device checks the information and verifies the signature (making sure it really came from Apple because it CANNOT be forged as the encryption is very high). iTunes packages up this valuable information and sends it to your device. Apple takes the firmware version files and combines them with your ECID and generates a hash that ONLY APPLE can generate. It is signed with a unique id (ECID) that only your device has. See, the firmware is now signed for the below devices. The way they stop you is basically by a simple response that iTunes receives when you try to restore the firmware of your choosing. Once you ‘upgrade’ they don’t let you downgrade. Sorry for the super long post.maybe you didn't want to read that much.When you try to restore an older firmware on the devices listed below, Apple won’t let you do that. If you don't need to jailbreak, then I don't think it matters, you just won't be able to downgrade to anything, only restore to the current version. Oh, and there is no way to get these blobs from another 3G user because these blobs are unique to each phone.įinally, do you jailbreak/unlock your phone, or is it a non-modded phone? If you jailbreak or unlock I highly suggest that you download Tiny Umbrella and start saving your SHSH. There is no way for me to downgrade my iPhone 4 to anything lower than 4.2b3. So, I have an iPhone 3G with SHSH blobs 4.0, 4.0.1, 4.0.2, 4.1, but my iPhone 4 only has SHSH for 4.2b3 and 4.2.1 because I just got it last week. Once a new version is released, you can only save the blobs for the current version. Here's the problem: you have to save the SHSH blobs before a new version of the firmware is released. Basically (if I understand it correctly), when you want to restore you point iTunes to check with your machine or Cydia (instead of Apple), and if you have old SHSH blobs saved, iTunes will allow the restore process to proceed. These are what the "requests" that iTunes sends to the servers are looking for. There is a program called Tiny Umbrella, and what this does is save your "SHSH blobs" to your computer, and also to Cydia's server. There is a way around this, but in your case I am nearly positive you can't do this. So basically, Apple forces you to use the most current iOS. If iTunes doesn't have access to its servers, you just can't restore. "So can't I block iTunes' connection with Little Snitch or turn off my access to the internet?" you ask. If the servers see that you are trying to use an old firmware bundle, they deny your request and iTunes reports back that you can't restore with the selected firmware. What this means is that every time you try to restore your phone, iTunes sends a request to the Apple servers with the firmware bundle version that you are attempting to use. It *may* be possible, but I seriously doubt it, and here is why:Īs of now, Apple "signs" all new firmware bundles that they release.
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