Go to /private/var/root/Library/, delete original lockdown folder and put this lockdown folder after you extract it from the zip file
Restart phone
If you are not jailbroken:
Sherif Hashim discovered that you can activate your iPhone 4, iPhone 3GS or even iPhone 3G without the original carrier SIM card. You need a “phonebook sim card” or 02 simcard. You can buy these type of sim at radioshack, bestbuy or other mobile electronics store (for example here).
Once you get passed the Emergency Call screen, connect to Wifi, jailbreak using JailbreakMe.com and unlock using ultrasn0w. Once that is complete you should be passed activation and unlocked (able to use any sim). If you get a different simcard error, do the following final step:
Go to /private/var/root/Library/, delete original lockdown folder and put this lockdown folder after you extract it from the zip file
Restart phone
If you have itunes invalid response problem:
Connect to wifi and ssh to your phone (via winscp, putty, terminal, etc).
Navigate to your lockdown folder (/private/var/root/Library/).
Delete pair_records folder
Reconnect the cable and see that your invalid response problem is gone.
If you bought your iPhone 4 on ebay you will need the official sim (at&t) or a universal sim, like ones you can grab at bestbuy for $10 this will get you passed Emergency Screen.
DevTeam updated ultrasn0w. They removed the daemon and used ideas of GeoHot’s purplesn0w, but implemented these ideas in a better safer way. New ultrasn0w 0.9 uses 152 bytes of baseband RAM, which is 6900 timesless than purplesn0w. They also use mobile substrate to patch CommCenter, instead of patching the file itself.
Here is a list of features from DevTeam.
Works on both 3G and 3GS.
Works on hacktivated devices.
Works regardless of how you jailbroke your device.
Doesn’t patch any mach-o binary whatsoever. (Doesn’t require a separate patch as each new firmware comes out).
Doesn’t install any additional daemon
Has no race conditions, no popups about “Missing SIM”, no network issues
Is almost 7000 times smaller than its nearest competition