Yesterday, we told you about iFaith’s latest update, which adds support for all versions of Apple’s mobile operating system up to iOS 5.0.1, and recommended that users download the software, save their SHSH blobs and build a custom IPSW file for safekeeping. Now, we’re going to walk you through the entire process, just so everything makes perfect sense.

(Please note: iFaith is compatible with Windows computers only; Mac users can download and save SHSH blobs using TinyUmbrella, though this program doesn’t save the all-important AP ticket. Furthermore, for obvious reasons, this method won’t work with the iPhone 4S.)

1 – Why you should do it

If you follow the below method, you’ll have created a custom IPSW that you can “downgrade” to in the future. For example, say you update to iOS 5.1, or even some future version of iOS 5 that you really don’t like (or that is “unjailbreakable”), following Apple’s rules, you won’t be able to install an earlier version of the iOS on your iOS device.

However, if you have a custom IPSW of iOS 5.0 or iOS 5.0.1, you’ll be able to dodge the strict Apple rulebook and downgrade to this firmware file, returning to an earlier version of the iOS. A lot of the time, people downgrade in order to jailbreak (because new versions of the iOS always take a little while – be it weeks or months – to “liberate”), and having a jailbroken iOS device to them is more important than having the latest update. Even if you aren’t interested in jailbreaking and don’t expect to ever downgrade an iOS device, it doesn’t hurt saving SHSH blobs and building a custom firmware file, just in case.

2 – Downloads

You’ll need iFaith and the stock IPSW firmware file of whatever version of iOS 5 you’re running. Here’s the webpage for iFaith’s download link. For the iOS firmware files, we recommend visiting iDownloadBlog’s Downloads webpage.

Alright, once you’ve got everything downloaded and installed, proceed to the next step in which we discuss saving one’s SHSH blobs.

3 – Saving SHSH blobs

You should have already downloaded and installed iFaith. Now connect your iPhone to your computer, open the program (as administrator) and put your iPhone into DFU mode. This can be achieved by holding the Lock button for three seconds, the Lock and Home buttons for 10 seconds, and then just the Home button for a further 10-15 seconds.

Next, click “Dump SHSH Blobs” and then “Proceed, Let’s Go!”

Following this, ensure that Apple TV 2 is deselected on the prompt. Now, iFaith will find your SHSH blobs and ask you for a save location: this can be anywhere, though the best place is probably your computer’s desktop. These SHSH blobs are incredibly important: back them up, even email them to yourself (as iFaith recommends!), but whatever you do, just don’t lose them!

4 – Building a custom IPSW

Now you have your SHSH blobs, the next thing to do is build a custom IPSW firmware file that you can downgrade to in the future. In order to do this, re-run iFaith and stick your iPhone into DFU mode (again), and select “Build *signed* IPSW w/ Blobs.” Following this, select your iOS device’s stock firmware file (which you should have already downloaded), and build the custom IPSW.

In order to restore to this custom IPSW, a “pwned DFU mode” is required. Luckily, iFaith can help with this: in the program, click “Proceed” and “Start,” and put your iPhone back into DFU mode. iFaith will then run iReb, which puts your iPhone into the all-important pwned DFU mode: a pop-up window will confirm that your handset is in this mode once the process has finished.

5 – Restoring to the custom IPSW

Finally, you can restore to the custom, signed IPSW you built in the above step using iTunes. Your iOS device, which should be in pwned DFU mode and already connected to your computer, will be recognized by iTunes: do not restore using the conventional method, but instead hold down SHIFT on your computer’s keyboard and click the “Restore” button in the device pane in iTunes.

Now, browse for the custom firmware file you built and saved in the above step, select it and let iTunes extract and restore the firmware.

6 – You’re done

Keep this custom firmware file safe, because you’ll be able to downgrade to it in the future. (In fact, if the firmware file you built was iOS 5.0, you can try updating to iOS 5.0.1 and downgrading just to see if the process runs smoothly.) Hopefully, the Chronic Dev Team will give us a reason to want to downgrade to iOS 5.0 or iOS 5.0.1 with the release of an untethered jailbreak solution for these versions of the iOS.

For a video walkthrough the above process, head over to iDownloadBlog.