Because the SEP firmware is rarely compatible across major iOS versions, saving blobs has become less of a "magic bullet." Even if you have the blobs for an old version of iOS, if the currently signed SEP firmware isn't compatible with that old version, the restore will fail or result in broken functionality, such as a disabled Touch ID or Face ID. Conclusion
: Most jailbreaks are version-specific. Saving blobs is your insurance policy; if you accidentally update or your phone crashes, blobs allow you to return to a jailbreakable version. Key Technical Terms iOS Guide: How To Downgrade And Save SHSH Blobs! shsh blobs
Over time, Apple has made this process increasingly difficult. While early devices (like the iPhone 4 and earlier) had relatively simple workarounds, newer hardware incorporates more complex security checks, such as "nonces" (numbers used once), which make saved blobs much harder to use without advanced technical knowledge. On many modern devices, blobs may even be rendered "useless" if the underlying firmware (like the SEP) is no longer compatible. Conclusion Because the SEP firmware is rarely compatible across
If Apple still supports that version, its servers return an SHSH blob—a digital signature that "greenlights" the installation for that specific hardware. Because these blobs are unique to each individual device’s ECID, a blob saved for one iPhone cannot be used on another. When Apple releases a new iOS version, they typically stop "signing" older versions after a few weeks, effectively closing the "signing window" and preventing users from ever going back to an older firmware. The Golden Age of Downgrading Key Technical Terms iOS Guide: How To Downgrade
SHSH blobs are a critical component in the history of iOS customization, representing the ongoing "cat-and-mouse" game between Apple’s security engineers and the jailbreak community. To understand them, one must look at how Apple controls the software lifecycle of its devices and how users have historically bypassed these restrictions to maintain control over their hardware. The Purpose of SHSH Blobs
—a random, one-time-use number generated by the device for every restore request.
Furthermore, the SEP passcode mechanism is designed to protect your data if the phone is stolen. Downgrade attacks (like "Checkm8") historically allowed thieves to bypass Activation Lock by downgrading to an old, vulnerable version of iOS. Apple closed this hard.