You've done nothing to address OP's concerns. The linked twitter thread assumes each actor (NCMEC, FBI, Apple) act in a certain way. There's no "provable" guara

You've done nothing to address OP's concerns. The linked twitter thread assumes each actor (NCMEC, FBI, Apple) act in a certain way. There's no "provable" guarantee against an actor acting in bad faith or in a manner inconsistent with certain interpretations of the law (which we've seen routinely with the NSA). The FBI/NSA can absolutely inject something into the hash list. You're assuming that NCMEC needs to be involved. Or that it would be broadly known to Apple. The reality is that the hash list needs to be updated on a different cadence than iOS itself. So it's likely downloaded rather than baked into the OS build permanently. That means that you can't necessarily rely on an iOS build being signed to know if you have a different hash list from everyone else. Ultimately, a small team at Apple cooperating with a secret court order could release a different hashlist to a select set of devices. There's nothing really stopping that. Even if Apple didn't comply, we've seen recently how sophisticated cybersecurity companies armed with zero days can manipulate devices easily. If the mechanism for hash lists scanning the device is already built in all it takes is an exploit changing the hashlist and where it reports to which might be much simpler than gaining full access to the device.