Question about SHSH blobs...

[gravytrain84]

Yesterday I was finally able to figure out how to restore my ip4 and keep 4.0.1 firmware running. The question I have is, what exactly does TU do if I am DL the firmware and installing via iTunes? How are the shsh blobs being used there? Is TU only used to kick iPhone out of recovery mode in this instance?

 

[TMar]

Tu replicates Apple's signature server. itunes asks these servers if x.x firmware is authorized for restore and as of right now Apple is only allowing restores of 4.0.2. TU/cydia pretends to be Apple's server and return's the authorization for saved blobs. This is what SHSH hashing is for. It stores the reply OK from Apple for a given firmware allowing another server to return these in place of Apple's at a later time.

 

[Myzhi]

Normally, when you try to install a firmware, iTunes connects to apple server, sends SHSH blobs if allow / deny your request. Of course, it will only allow current firmware, now 4.0.2, and deny everything else. With Tinyumbrella => local or changing host file => Cydia server, tricks ITunes into thinking it's connected to apple server when it's not and allow you to install older firmware. That's the basic for it.

 

[gravytrain84]

Thanks for the explanation guys. So as long as TU is up and running, it'll trick iTunes into thinking it's on the server? If I were to dl firmware and try to install without TU open, it would deny?

 

[TMar]

Yes, when it running it just intercepts the requests and returns the the cached 'OK'. If it's not running the request goes to Apple's server and is denied.

 

[gravytrain84]

Yes, when it running it just intercepts the requests and returns the the cached 'OK'. If it's not running the request goes to Apple's server and is denied.

Genius

 

[gravytrain84]

One more question fellas... If i am doing a restore with a d/l version of 4.0.1 and I have TU open but do not 4.0.1 SHSH, it would not work, right? You have to have the d/l firmware, the shsh in TU, and itunes all working together?

 

[f4780y]

One more question fellas... If i am doing a restore with a d/l version of 4.0.1 and I have TU open but do not 4.0.1 SHSH, it would not work, right? You have to have the d/l firmware, the shsh in TU, and itunes all working together?

Correct. TU must return your real SHSH for 4.0.1 which was created by Apple for you sometime in the past. There is no way to spoof an incorrect version which is why it is so important to have your SHSH's saved...

 

[TMar]

One more question fellas... If i am doing a restore with a d/l version of 4.0.1 and I have TU open but do not 4.0.1 SHSH, it would not work, right? You have to have the d/l firmware, the shsh in TU, and itunes all working together?

Redundant, this was emphasized in post #2. Stored hashes are device and firmware specific.