Apparently not much and the title seems to be wrong (unless there’s more the I didn’t see). According to people in that Twitter thread it’s the public part that

Apparently not much and the title seems to be wrong (unless there’s more the I didn’t see). According to people in that Twitter thread it’s the public part that’s just extracted from iBoot which ships on every iOS device [1]. It doesn’t let you sign your own boot loaders. [0] https://twitter.com/aydenpanhuyzen/status/1332084351039889412?s=21 https://twitter.com/aydenpanhuyzen/status/133208435103988941... [1] https://twitter.com/matteyeux/status/1332083960172703750?s=21 https://twitter.com/matteyeux/status/1332083960172703750?s=2...