TinyUmbrella has been updated to support iPhone 4 (running iOS 4). It is important to save SHSH Blobs (ECID SHSH) files of your iPhone 4 now because of all the rumors going around regarding a new firmware update, which could be released as early as next week. If you have your SHSH blobs on file, you can downgrade anytime to iOS 4 from iOS 4.01 should you need to.
Some important notes for iPhone 4 SHSH blobs before you proceed.
In order to obtain your SHSH you MUST have the device attached.
Restores on the iPhone 4 are not perfect. They error out locally but the restore does complete – it just needs to be helped along. (Much like downgrades where the baseband update fails). I’ll try to put the functionality in TinyUmbrella to fix this.
For Mac users: Copy the app OUT OF THE DMG. The reason you are getting the repeating password prompts is because you ran the app from within the DMG. This is bad. Copy it anywhere and you’ll be fine.
From here onwards, you can simply follow the steps that i have posted here for iPhone 3GS and iPod touch. These steps are essentially the same for iPhone 4 except for some of the notes that I have posted above. Oh and if you want to learn more about what SHSH blobs or ECID SHSH files are, you can do so by reading one of my old article posted here.