Downgrade with Checkra1n

[pscullum]

I have an iPhone 6s with SHSH2 blobs saved for every iOS version since iOS 9. I am on 13.3 jailbroken with checkra1n. Is there a nonce setter available for the iPhone 6s using the checkm8 exploit? I know of a few available on GitHub but none seem to support the 6s at the moment ☹️. Can I set the nonce in terminal since I’m jailbroken? If so...How? Thanks for any help in advance

[GeoSn0w]

There might be ways to set the nonce, but you still won't be able to downgrade to iOS 9 / 10 / 11 / 12 at the moment using CheckM8 or CheckRa1n because the SHSH2 blobs aren't all it takes. See, the SEP. (Secure Enclave Processor) which handles Touch ID / Face ID, Passcode, Filesystem Encryption, and on-device keys have to also be downgraded or you need to use a compatible latest version from iOS 13.3 for example. iOS 13.3's SEP isn't compatible with older versions and downgrading SEP is currently not possible without breaking it.

There's also the Baseband component which handles the cellular connections (2G, 3G, 4G, VoLTE, etc.) and this cannot be downgraded safely either. They're signed and verified.
Progress is being made towards a full downgrade but for now, tethered downgrades are what we can get and such downgrade won't allow you to even power on your phone without having a Mac / Computer with CheckRa1n nearby.

[pscullum]

Thanks GeoSn0w! I have successfully used future restore in the past. I went from 11.3.1 to 12.1.2. I used it to update to unsigned firmwares when unc0ver was updated. I’ve watched the video where someone successfully got tfp0 on 13.3. My goal here is to move back to unc0ver as quickly as possible and I thought 13.2.3 might be a better firmware to wait for unc0ver. I will just wait for more tools to be released or stay on 13.3 and wait for unc0ver. It’s a very easy wait because I’m jailbroken and the latest version of checkra1n is rock solid.