Need clarification to downgrade firmware for 3GS

I have been following all the threads and postings on iclarified regarding unlock/jailbrea.

From what I understand so far, 3G and 3GS that have been upgraded to Version 3.1.3 with Firmware 05.12.01, currently there is NO WAY to unlock, only jailbreak.

However, there is posting on iclarified to downgrade firmware to an earlier version (assuming the phone has been previously jailbroken and unlocked before).
iClarified - iPhone - How to Downgrade Your iPhone 3GS Using a Cydia Saved SHSH [Mac]

Does it really mean one can downgrade firmware from 05.12.01 back to 05.11.07, thereby making this possible to unlock?

Would someone please clarify this.

Quote:

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Originally Posted by sfaguy

From what I understand so far, 3G and 3GS that have been upgraded to Version 3.1.3 with Firmware 05.12.01, currently there is NO WAY to unlock, only jailbreak.

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A 3GS once upgraded to 3.1.3, there is no way to DIRECTLY jailbreak. You need to downgrade first if possible. As you state later.

Quote:

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Originally Posted by sfaguy

However, there is posting on iclarified to downgrade firmware to an earlier version (assuming the phone has been previously jailbroken and unlocked before).
iClarified - iPhone - How to Downgrade Your iPhone 3GS Using a Cydia Saved SHSH [Mac]

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yes you could have used Cydia to back up your SHSH but it was not the only way.

You actually did not need to have jailbroken or unlocked before. All you need is to have been smart and either restored using an older version of iTunes (capturing the tmp directories created during restore) or put the phone into DFU mode, grabbed the ECID, rebooted the phone out of DFU mode and then used firmware umbrella to grab your SHSH.

Now it is all too late because Apple has stopped signing 3.1.2

Quote:

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Originally Posted by sfaguy

Does it really mean one can downgrade firmware from 05.12.01 back to 05.11.07, thereby making this possible to unlock?

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Your idea is wrong. Apple's security model is more restrictive with baseband. there is generally no way to downgrade it (or even restore the same version)

For 3GS, no
For 99% of 3G iPhones, no

The other 1% of 3G iPhones can try iClarified - iPhone - How to Downgrade Your iPhone 3G Baseband Using Fuzzyband

Quote:

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Originally Posted by Olethros

A 3GS once upgraded to 3.1.3, there is no way to DIRECTLY jailbreak. You need to downgrade first if possible. As you state later.

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If this is the case, why iclarified posted a link to jailbreak 3GS for FM 3.1.3? Plus they did not mention anything about downgrade first.

iClarified - iPhone - How to Jailbreak Your iPhone 3GS Using PwnageTool [Mac]

Quote:

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Originally Posted by sfaguy

If this is the case, why iclarified posted a link to jailbreak 3GS for FM 3.1.3? Plus they did not mention anything about downgrade first.

iClarified - iPhone - How to Jailbreak Your iPhone 3GS Using PwnageTool [Mac]

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Although not clearly stated, this guide only works with either 3.1.2 or 3.1 (not jailbroken) or 3GS that are already jailbroken (running any 3.x OS, including 3.1.3 already jailbroken).

This guide was quickly updated from the Pwnagetool 3.1.4 / OS 3.1.2 guide. In my opinion, this was the wrong approach it should not have been updated a new guide should have been written instead.

Pwnagetool only works with old bootrom 3GS. The technique it uses is incompatible with tethered jailbreaks. If you have a new bootrom you need to use redsn0w 0.9.2 or blackra1n (both only work up to 3.1.2 on the 3GS)

A 3GS (old or new bootrom) once upgraded or restored to original Apple 3.1.3 (not custom IPSW) can no longer be directly jailbroken. The only way to jailbreak again is to use a saved SHSH for 3.1.2 or lower to downgrade. Once downgraded, the various jailbreaking tools (redsn0w, blackra1n, pwnagetool etc) will work