If you save these blobs while a version is still being signed, you can use them later to trick iTunes (or other tools) into installing that "expired" version. Why You Should Save Them
If the currently signed SEP/Baseband is , the restore will either fail, brick your device, or cause critical features like Face ID and cellular signal to stop working entirely.
When Apple introduced the SHSH blob system during the era of the iPhone 3GS, it was a static signature challenge. In those early days, saving a blob meant capturing that static file and replaying it to iTunes via a local proxy server (such as Cydia's TSS server or TinyUmbrella).
Apple checks if that version is still "open." If it is, they send back an SHSH blob. shsh blobs
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An SHSH blob is simply that signature saved to a file (or stored on a remote service like Cydia’s server) before Apple stops signing the corresponding iOS version. Once saved, it can be reused to fool the local restore process into accepting an unsigned firmware.
You can only save blobs for iOS versions that Apple is . You cannot go back in time and save blobs for iOS versions Apple has already closed. Option 1: Using BlobSaver (Recommended) If you save these blobs while a version
During a custom restore process using saved blobs, the target iOS version must remain compatible with the SEP firmware of the currently signed iOS version. If the current SEP firmware is incompatible with the older iOS version you want to install, the restore will fail, or your device will boot without any biometric security functionality.
When a new iOS version patches a major vulnerability, Apple quickly stops signing the older version. This prevents users from downgrading to a vulnerable firmware version.
While SHSH blobs no longer pose a practical security threat to average users, they highlight the importance of server-side signature enforcement combined with hardware-rooted entropy—a design principle Apple has successfully strengthened. In those early days, saving a blob meant
SHSH blobs are the crucial link between your iOS device and Apple's authorization servers. By understanding what they are and creating a habit of saving them, you maintain control over your device's firmware, allowing for potential downgrades and future jailbreaking opportunities.
But what are they, why are they necessary, and how do they work? This article provides a comprehensive guide to understanding SHSH blobs, their role in Apple's security architecture, and how to manage them. What Are SHSH Blobs?
Your device's bootloader checks this blob. If it matches, the installation proceeds. How to Save SHSH Blobs
Disclaimer: Modifying iOS firmware violates Apple’s EULA and may void your warranty. Always back up your data before attempting any restore with SHSH blobs.
Apple uses these signatures to "sign" a specific firmware version for your specific device.