X-Gold 608 Unlock

Until recenlty, the 3G software unlock was the biggest missing piece of the iPhone community. It proved more difficult than the previous unlocks due to the fact that the baseband bootloader is signature checked by the bootrom. The dev team has successfully unlocked all baseband versions less or equal to 02.28.00, by overriding carrier locks on-the-fly in RAM, therefore at boot the baseband bootrom can validate the bootloader, and the bootloader can validate the baseband. The unlock, code-name yellowsn0w, was released to the public on 01/01/09 for baseband 02.28.00 only [1]. ultrasn0w, an updated version of yellowsn0w, which uses a different injection vector and available for all baseband versions less or equal to 04.26.08, is planned to be released on June 19, 2009.

Possible Methods

Class 1

• Find an exploit in the bootrom to break the chain of trust. The Dev-Team successfully dumped the bootrom, but they won't release it as it's copyrighted code.
• 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 yellowsn0w. Geohot and The dev team found (independently) an exploit in bootloader 5.8, but it isn't useful enough as only very-early (week<30) devices have bootloader 5.8.

Resources

• Read about the X-Gold 608
• Read geohot's blog post
• 25C3 presentation "Hacking the iPhone" video here