Unlock iPhone 4 for iOS 4.3/4.2.1 with Gevey SIM Interposer

Unlock iPhone 4 for iOS 4.3/4.2.1 with Gevey SIM Interposer

Here is the good news atleast for the time being for all those people who own a locked iPhone 4 with iOS version 4.3/4.2.1 on 2.10.04/3.10.01 baseband. The Gevey team has announced an unofficial way of unlocking your iPhone 4. According to the team, the phone is unlocked by forcing the activation of the baseband using the emergency dialer, and this applies upto the version of 4.3. This is done with the help of a device called SIM interposer, which is placed between the SIM and the baseband hardware.

Working of the Unlock

  • SIM card holds many different types of information, but the part most involved with carrier lock is the IMSI number, which is a unique code that corresponds to your account in the mobile carrier’s database.
  • A sample IMSI might look like this310 150 987654321The first two segments are known as Mobile Country Code (MCC) and Mobile Network Code (MNC) respectively, and in the example above the IMSI indicate the SIM is from USA (310) AT&T (150).
  • When the iPhone baseband is loaded into memory, it checks the MCC and MNC against its own network lock state stored in the seczone. If the combination is allowed, the cell radio is activated and vice versa.
  • The earliest iPhone baseband revisions only check IMSI twice following a restart, therefore it is very easy to send spoof information in order to bypass the check. Nevertheless, the baseband was soon updated to validate SIM more aggressively and the method soon became obsolete.

Unlike its previous devices, the iPhone4 SIM interposer is not a drop-in-and-forget device. The exact precedure must be performed should the device restart, lose reception for an extended period of time or move to another PLMN. In all these situations the TMSI expires and has to be obtained again. Theoretically it is possible for a daemon to automate the process similar to ZeroG, but that only makes thing more convoluted.

It is, without question, unethical or downright illegal to use the technique anywhere 112 is a legitmate emergency number. This is never an huge issue in China where the number is only used for informative purposes and the networks cannot be bothered to fix the issue. All firmware/baseband combinations for the i4 up to iOS4.3 are vulnerable, however the exploit may be patched in any future software updates or via the carrier. If apple can influence providers to block Cydia it is not impossible for them to press them to fix the exploit. The only way to permanently unlock your baseband is NCK. SIM interposer doesnt harm the phone, but your network could request IMEI and identify your device during the emergency call. Your identity cannot be faked and it is possible that they might suspend your account.

If you can no longer wait for the unlock for your iPhone, then you might give this procedure a try. The source also says that a 40-bit NCK iPhone 4 hack will be out anytime from now by the Dev Team.

Do checkout the video about the working of the Unlock iPhone 4.


Source: Singularity

Article by Venkatesh Atluri

Venkatesh has written 24 articles.

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{ 2 comments… add one }

  • Andy

    May 9, 2011, 10:26 am

    I did it with Gevey SIM to unlock my phone. My iphone 4 was accidentally SIM lock and i don’t have the original SIM card to pass the emergency screen when i accidentally upgrade to 4.3.1. Then i manage to down grade to 4.1 and I did the jailbreak and then using Gevey SIM interposer to unlock my iphone 4. It works!! If you need help to get Gevey SIM interposer. I can help!

  • Rav

    June 3, 2011, 7:14 am

    Thanks for an informative blog. Would you have any idea as to how I can activate face time on my iPhone 4 running of fw 4.3.1 in India on gevey sim. I bought my phone from the UK 2 months ago. I have tried face break, mistime and altering the carrier bundles but I still get the ‘ waiting for activation’ message when I try to activate FaceTime.

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