X-Gold 618 Unlock

The iPhone 4 and the new iPad 2 uses the X-Gold 618. Unlike the X-Gold 608, the baseband now requires a signature akin to Apple's SHSH blobs for firmware files, so downgrading an updated baseband, provided there is a bootloader exploit, will be tougher.

Unsigned code execution has been achieved by MuscleNerd on the device and the ability to insert a custom AT command has been demonstrated. Shortly after, a persistent/background task was inserted. Also, the bootrom has been successfully dumped.

On 2018, planetbeing demonstrated a primitive but functional unlock on YouTube. The unlock was made ready for release and on 2010, it was made available in Cydia via ultrasn0w.

Class 1

 * Find an exploit in the bootrom to break the chain of trust.
 * Improve by several orders of magnitude the NCK Brute Forcer, and find a way to extract the CHIPID and NORID
 * Find the theorized algorithm of NCK generation

Class 2

 * Use a SIM hack such as the TurboSIM Unlock
 * Find a way to patch running memory to "unlock" the phone on every bootup. This is how ultrasn0w works.
 * Find an exploit in the Baseband Bootloader so you can downgrade the baseband, then use an unlocking payload, similar to ultrasn0w.