how can i upgrade to ios 4.3 (latest ios) from ios 4 on a 3gs and keep my jailbreak?
The latest jailbreakable (untethered) firmware is 4.3.3
Apple is still signing (allowing restore to) firmware 4.3.3 but it will surely stop very very soon in like 24 hours due to 4.3.4 being public, so its urgent you do the upgrade to 4.3.3 ASAP (like right NOW), otherwise you can save Apple's signature (authorization) of 4.3.3 for a later replay by using TinyUmbrella found here (http://thefirmwareumbrella.blogspot.com/).
You will need to download the 4.3.3 firmware for your device, the below Apple link is for iPhone 3GS:
Once downloaded, hold the SHIFT key (or ALT/Option key in Mac) while you click the RESTORE button in iTunes, next select the ipsw file downloaded above, the restore will go through without problems if you do it NOW.
TinyUmbrella can save your SHSH blobs for later replay, just connect your iPhone and hit the Save SHSH. at a later time you can replay the SHSH if you start the TSS server within TinyUmbrella and do the SHIFT+RESTORE to 4.3.3 ipsw.
Note: Windows Internet Explorer automatically changes the .ipsw extension to .zip, you need to rename it back to .ipsw if you're affected.
answered 18 Jul '11, 02:12