Can i upgrade 4.3.1 & unlock with redsn0w?

[Datastream]

I am on 4.0.1 (05.03.04) already with unlock. Can i use redsn0w v0.9.6rc12 to upgrade straight to 4.3.1 without downgrading or going back to stock and do i have to backup my SHSH Blobs if I already used Cydia.

[goofball2k]

what do you mean "without downgrading"?
Your best bet is to download the 4.3.1 ipsw and snowbreeze 2.5.1. Use snowbreeze to create a custom ipsw so you maintain your unlockable baseband. Then upgrade to 4.3.1 using that custom ipsw. It will be jailbroken as well.

[kofster]

Data Stream, you sound fresh. There is now way you can upgrade to 4.3.1 using redsn0w. redsn0w is used only to jailbreak the iOS file system once it has been already uploaded to the iOS device. If you are a windows user, do like goofball2k says; download sn0wbreeze and the ipsw for your device. Use sn0wbreeze to create a jailbroken ipsw that won;t have the baseband unlock in it and restore using that custom jailbroken ipsw in iTunes. You only need to use redsn0w if you have an iPhone 4 that can be upgraded to 4.3.1 without updating the baseband with the help if TinyUmbrella or you are with a carrier and having an unlock is not a priority for you.
Please make sure you stay away from redsn0w.

[changsternation]

yeah