Last week, the hacker Tihmstar announced the Prometheus app that allows you to downgrade the operating system on your iPhone or iPad. We are talking about OS versions that are no longer signed by Apple. The main condition for the successful application of Prometheus – pre-saved SHSH blob.
SHSH blob is a digital signature file, which Apple checks the version of iOS on the device. To use Prometheus is not suitable certificates that have been saved using TinyUmbrella or savethemblobs. The necessary files in a special format shsh2, they can be obtained by the utility Tsschecker.
How to use Tsschecker to retrieve a certificate for the iPhone and iPad later in our instruction.
How to save .shsh2 blobs using TSSchecker:
Step 1: Download the utility Tsschecker from this page (Mac, Windows, Linux) and extract the application from archive.
Step 2: On your desktop create a folder TSS and put the unzipped file tsschecker.
Step 3: Open TextEdit and connect your iPhone or iPad to your computer.
Step 4: Open iTunes and navigate to the devices page.
Step 5: On the main page of iTunes we need to find the ECID and model ID of the connected device. You can recognize them by clicking on the field Serial number.
Step 6: Copy the two paragraphs in TextEdit. In our case, the model ID “iPhone7,2”, and “ECID” – “1234A8956dB162”.
Step 7: Copy the following lines into a text document:
/Users/USERNAME/Desktop/TSS/tsschecker -d ID -e ECID -10.2 i-s
/Users/USERNAME/Desktop/TSS/tsschecker -d ID -e ECID -10.1.1 i —buildid 14B150 -s
/Users/USERNAME/Desktop/TSS/tsschecker -d ID -e ECID -10.1.1 i —buildid 14B100 -s
/Users/USERNAME/Desktop/TSS/tsschecker -d ID -e ECID -10.1 i-s
Step 8: We need to replace the words written in capital letters. Instead of the USERNAME indicates the account name, ID, change it to “iPhone7,2” and ECID – “1234A8956dB162”. Do this for each of the four lines.
Step 9: once everything is ready, open a Terminal.
Step 10: Run the following command
chmod +x ~/Desktop/TSS/tsschecker
Step 11: Now tsschecker should be executable.
Step 12: Copy every line of the document TextEdit turns into the Terminal, pressing Enter after each line. The result should be similar to the following:
Step 13: After performing these steps, you will be saved file format shsh2. This is a digital certificate blobs for iOS 10.2, iOS iOS 10.1.1 and 10.1.
Step 14: just In case you can re-run the above command, adding the parameter apnonce. This will help to increase the chances of a downgrade in the future.
For example, the command would be like this:
/Users/macdigger/Desktop/TSS/tsschecker -d iPhone7,2-e 1234A5678B912 -10.1 i-s —apnonce 9804d99e85bbafd4bb1135a1044773b4df9f1ba3
These commands will overwrite the files you already have saved. Therefore, pre-transfer them to another location. Look for saved files need in the folder /Users/USERNAME next to the folders Documents and Download.