SHSH blob

In <a href="/facts/Computing/Kghtm9fX">computing</a>, a SHSH blob, short for Signature HaSH blob, is a <a href="/facts/Digital_signature/tY7e2pnW">digital signature</a> that <a href="/facts/Apple_Inc./oTJYta3k">Apple</a> generates and uses to control the iOS versions that users can install on their iOS devices generally only allowing the newest iOS version to be installable. Apple's public name for this process is System Software Authorization (before <a href="/facts/IOS_7/LP8uLlwP">iOS 7</a>, System Software Personalization). The term “SHSH blob” is unofficial and based on abbreviations for <a href="/facts/Digital_signature/tY7e2pnW">signed hash</a> and <a href="/facts/Binary_large_object/BzGnvlgo">binary large object</a>. An alternative term, ECID SHSH, refers to the device's ECID, a unique identification number embedded in its hardware.
This process is controlled by the TATSU ("TSS") Signing Server (gs.apple.com) where updates and restores can only be completed by <a href="/facts/ITunes/pdXPE33T">iTunes</a> if the version of iOS is being signed. Developers interested in <a href="/facts/IOS_jailbreaking/yJxsE1h9">iOS jailbreaking</a> have made tools for working around this signature system in order to install jailbreakable older iOS versions that are no longer being signed by Apple.

SHSH blob open-in-new

SHSH blob