This page describes a “last-ditch” way to prevent a baseband update for those who ignored the warnings on http://spiritjb.com to not use Spirit if you're using blacksn0w on an iPhone 3GS without 3.1.2 SHSH blobs on file.
This is not a jailbreak or an unlock by itself. It's much safer than the “pull your USB cable during Firmware Update” method that's making its way around the forums (that method has the potential to brick your baseband if your timing is off).
Some people who were using blacksn0w on their iPhone 3GS at 3.1.2 tried to apply the Spirit JB without removing blackra1n despite all the warnings against this. Those who did usually found themselves in a reboot loop or stuck at the Apple or recovery screen. If they did this on an iPhone 3GS without 3.1.2 SHSH blobs on file, they got stuck with an inoperable phone. That's because restoring to stock 3.1.3 (to get out of the loop) also updates the baseband past the point where the currently released unlocks will work.
The number of iPhone 3GS jailbreakers using blacksn0w who do not have 3.1.2 SHSH hashes on file with Cydia is probably very small. Do not use this method if Cydia has your 3.1.2 SHSH hashes on file – it's overkill! Just restore to 3.1.2 using your saved hashes instead. (But if you've already got 3.1.3's baseband on your iPhone, it's already too late for you and you must wait for the next unlock. This method doesn't change that.).
Only use this method if you meet *all* of these requirements:
This method “mostly” restores to 3.1.3, but makes the restore process error out at a safe point by removing the LLB image from the stock IPSW. The error will occur before the NOR is erased and before the baseband is reflashed.
<key>LLB</key> <dict> <key>BuildString</key> <string>iBoot-636.66.33~4</string> <key>Info</key> <dict> <key>IsFirmwarePayload</key> <true/> <key>Path</key> <string>Firmware/all_flash/all_flash.n88ap.production/LLB.n88ap.RELEASE.img3</string> </dict> <key>PartialDigest</key> <data> QAAAADgBAQBmTeQNOchSWUN8/P56yjPVrrML 2w== </data> </dict>
Do this removal twice…once in the first half of the file, and once in the second half.
% rslite rslite v0.2 - by the iPhone Dev Team, 2009. --THIS IS AN UNSUPPORTED TOOL-- Connecting... [Recovery] setenv auto-boot true [Recovery] saveenv [Recovery] reboot
Feel free to send any general questions about this method to Musclenerd on twitter. (Please read and re-read this page before doing that though). And for general jailbreaking/unlocking tips and help, you can always visit our blog at http://blog.iphone-dev.org and follow our team twitter at http://twitter.com/iphone_dev