I read from many posts about "on file" process on Cydia's server.
Can I do any different process since I have all the required files and security information of my hardware?

My iPhone is locked 3GS with 3.0 OOTB but I used ultra and red to unlock and jailbreak. Now searching through some forums for 3.1 update and got a little bit confused. Pwnagetool is for Mac to create the custom FW without updating the baseband; does this tool requires iBEC, iBSS, or ECID in order to create the custom firmware?

Still not quite understand "on file" thing on Cydia's server. If those files are the same as my iBEC, iBSS, or ECID can I utilize my files and some tool to jb/unlock (OK if I stay on the old baseband I need no unlock...)

Please educate me.

One more thing, I experienced since the time of iPhone Classic about incompatibility between the new FW and the old baseband. Wouldn't it be any problem if we upgrade FW to 3.1 but still keep the baseband 04.26.08?????

I assume that in order to prevent hacking to the baseband, Apple changes the baseband to be non-programmable, or most likely. So it means to keep backward compatibility to the old hardware, the baseband must be at minimum change. Please feel free to correct my assumption.

Well, this is all what I know. Hope it helps to you.

I guess your mentioned iBEC/iBSS of your 3GS is for FW3.0 only. Coz FW3.1 has the different iBEC/iBSS.

1. So far, I haven't heard any utilities/tools convert iBEC/iBSS files onto Cydia's server by 'on file' format, although I believe both have the same signature data.

2. You can update your 3GS to FW3.1 by using a custom FW created by Pwnagetool 3.1.3. This process doesn't require any iBEC/iBSS or 'file' on Cydia's server. After this, you will get your 3GS in FW3.1 with baseband 04.26.08. Then you can unlock it by current Ultrasn0w;

3. On jailbroken/Unlocked FW3.1, you will not have your carrier's name showed normally(This is caused by the old baseband in the new FW). 'MakeItMine' on Cydia's server can solve this problem, or you can manually modify the file 'carrier.plist' on your 3GS.

Thanks a lot.
Your answers remind me the reason stated in the instruction of getting iBEC, iBSS, and ECID that they are used for downgrade back to FW3.0/3.0.1. I forgot that.