With the new loktar_sun trick to unlock iPhone 4 using Subsciber Artificial Module (SAM), it is now possible to trick Apple servers to activate non-official sim on locked iPhones. As pointed by @Musclenerd, the loophole maybe temporary and it is best to backup activation records once the iPhone is unlocked. Redns0w (Redsnow) 0.9.10b8 has been released by dev-team to do just that, backup activation tickets after iPhone is unlocked.
Here is a step by step guide to backup activation records using redsn0w (redsnow) 0.9.10.b8:
- Download redsn0w (redsnow) 0.9.10b8 : Download for Windows or Download for Mac
- Open redsn0w, goto Extras > Even More > Backup
- Thats it. Redsn0w will save your Activation records to make your unlock future proof.