For those who want to save their 5.3 signatures, here's a process that ABSOLUTELY works. It's honestly a bit of a pain in the arse since the process must be done on an un-jailbroken 5.3, but it WILL work! I have now done it 25+ times.
All credit for this solution goes to Ian82 who was gracious enough to provide it for me in an earlier post. This trick" has been "buried" here and truly deserves its own subject and spotlight.
The beauty of this process is that after you have been successful, you can immediately verify the saved signatures on the iFaith server.
Many will be kicking themselves for not having pursued this once Apple stops signing 5.3.
Here's how it's done:
1) Using Seasonpass, create an IPSW for the 5.3 unit whose signatures you want to save.
2) Exit SP once you are asked to enter DFU mode.
3) Run iReb (inside of iFAITH 1.5.9) and Pwn the ATV in DFU mode.
4) Run iTunes. Alt + Restore. iTunes will restore ATV to 5.3 vanilla (and un-jailbroken).
KEY TIP: When restoring with iTunes, be sure you are choosing the vanilla IPSW file in the my documents/seasonpass/DOWNLOADS folder -- NOT the patched IPSW with the letters SP in the file name that lives in the directory in the my documents/seasonpass folder. This is critical or your process will fail.
5) Once iTunes has finished restoring the Apple TV back to a factory-reset UNJAILBROKEN 5.3 , NOW run iFaith 1.5.9 and dump blobs in the old fashioned way… It can now be done!
6) When finished, verify that the 5.3 signatures have been saved on the iFaith server.
7) Now using Seasonpass, jailbreak on version 5.3.
For me at least, iFaith 1.5.9 remains "temperamental" in terms of completing the dumping process -- it still takes me 5 to 10 attempts at least. But for those frustrated and wondering after multiple failed attempts if dumping the blobs is even possible.... IT IS! Be persistent.