Shsh Blobs -

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.

: Modern blobs often require a specific "Nonce" (a number used once). Unless your device is jailbroken or you have found a way to "set" your device's nonce to match your blob, the blob is often useless. How To Check What SHSH Blobs You Have - iPhone, iPod, iPad shsh blobs