PwnageTool 5.1.1 allows to create custom firmware and preserve modem version for unlock with ultrasn0w or Gevey. PwnageTool 5.1.1 supports all A4 devices:
iPhone 3GS
iPhone 4
iPad 1
iPod Touch 3G
iPod Touch 4G
Apple TV 2G
You can download RedSn0w 0.9.12b1 here and PwnageTool 5.1.1 here.
The iPhone Dev-Team has updated RedSn0w with the ability to save iPhone unlock tickets (SAM unlock).
redsn0w 0.9.10b8 adds the ability to backup arbitrary directories or files from your device into a zip file on your Mac or PC. The new button is Extras->Even More->Backup and it requires your device to be jailbroken with the afc2 service enabled (most jailbreaks include that). By default it will backup your activation records from /var/root/Library/Lockdown, which is useful for everyone taking advantage of today’s SAM unlock using Loktar_Sun’s trick
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.
Sn0wBreeze 2.9.6(pwnagetool for windows, supports untethered jailbreak of iOS 5.1.1 for iPhone 4, iPhone 3GS, iPod Touch 3G, iPod Touch 4G, iPad and Apple TV 2G)
Sn0wBreeze 2.9.3(pwnagetool for windows, supports tethered jailbreak of iOS 5.1 for iPhone 4, iPhone 3GS, iPod Touch 3G, iPod Touch 4G, iPad; untethered for iPhone 3GS with old bootrom; untethered for iOS 5.0.1, iOS 4, iOS 3 supports Apple TV 2G)
Sn0wBreeze 2.8b11(pwnagetool for windows, supports iOS 5, iOS 5.0.1, tethered jailbreak for iPhone 4, iPhone 3GS, iPod Touch 3G, iPod Touch 4G, iPad, Apple TV 2G; untethered for iPhone 3GS with old bootrom)
Current version is ultrasn0w 1.2.3, download in Cydia (unlock for iPhone 4, iPhone 3GS, iPhone 3G, firmwares 3.0-4.3.3; it supports basebands 01.59.00, 04.26.08, 05.11.07, 05.12.01, 05.13.04, 06.15.00)