There is a lot of information on the net about unlocking solution like Gevey Sim. But there is not much info about how Gevey and other Sim hacks work. So here I decided to describe you essence of hardware-based unlocking method and show how it works. Gevey is a Sim Interposer that holds critical information like the IMSI number. IMSI number is a unique code that corresponds to your account in the Carrier’s database. IMSI has 15 numbers and every number means something: 475 230 834769475 Where 475 is Mobile Country Code (MCC) and 230 is Mobile Network Code (MNC) or Carrier. If the iPhone baseband is loaded into storage, it verifies the MCC and MNC next to its own network lock state kept in the seczone. When the combination is authorized, the cell radio is activated. Earlier before IMSI was checked two times following reboot. But today first connection to a network doesn't only include IMSI, although a 4-byte TMSI to determine each device before IMSI is shipped processed. The base station then transfer a 16-byte nonce towards the handset, where's signed with a 128bit DES key (Ki, kept secured on the SIM) and delivered back. The network inspected the chain against their database and enables that number to attach to the network. The thing is, the IMSI isn't important; providing that your key is legitimate, you will be able to get service. This is just what the different SIM hacks where a untrue IMSI is shipped combined with the appropriate key. The IMSI is redirected to a new network and lost, and the authorized nonce usually enables you to sign-up (devoid of cross-checking IMSI) Using this technique, “Data Roaming” has to be allowed to permit data connection as the baseband is functioning on the presumption that the phone is roaming nevertheless the network do appropriately identify the device as a home owner.

A Little History

SIM hacks always has been unreliable because the end result relies on the use of the hack along with the rules of the network; and folks were overloaded with a big list of problems and make shift methods. A standard solution is to regularly place the hacked SIM into jailbroken iPhone to “keep the link healthy”. Using SIM hacks dropped sharply after iOS 2.2.1 update where the new baseband were made mindful of the method and deny fake IMSIs, even better developed Interposers endured frequent problems. It's about once software unlocks were designed and it forced SIM hacks additional into disuse. Nevertheless the technology has been stored active since several GSM devices, primarily those originating from Japan, stays weak.