Unlocking Technology
A handset can be unlocked by entering a code provided by the network operator. Alternative mechanisms include software running on the handset or a computer attached to the handset, hardware devices that connect to the handset or over-the-air by the carrier. Usually the unlock process is permanent. One example is the Apple iPhone, which is officially unlocked (when applicable) every time during its activation step. The code required to remove all locks from a phone is referred to as the master code, network code key, or multilock code. There can also be multiple levels of locks placed on the phone by networks, which block the use of other networks SIM cards. These are usually referred to as "Network" (NCK) or "Service Provider" (SPCK) locks and can be removed using the corresponding unlock codes, which are unique to each phone depending on the its IMEI.
Typically, a locked handset will display a message if a restricted SIM is used, requesting the unlock code. For example, on the Sony Ericsson T610 mobile phone, "Insert correct SIM card" will be displayed if the wrong SIM is used. Other handsets may display different messages such as "Enter special code" or "Enter unlocking code" or in some cases the handset will simply display a message stating that it is locked. Once a valid code is entered, the handset will display "Network unlocked".
The unlock code is verified by the handset and is generated by the network provider, typically by an algorithm such as a one way hash or trapdoor function. The algorithms used in many handsets are based on the IMEI number and the MCC code and have been reverse-engineered, stolen or leaked. Most handsets can be unlocked using software that generates an unlock code from an IMEI number and country and operator details using the algorithm specific to the handset. Other manufacturers have taken a more cautious approach, and embed a random number in the handset's firmware that is only retained by the network on whose behalf the lock was applied. These handsets can still be unlocked, but need to be connected to special unlocking hardware that will rewrite the part of its firmware where the lock status is kept, and often even recover a phone that is bricked or completely damaged in the software sense. However, other handsets, notably the high-end PDAs and smart-phones, can be unlocked by the use of software that can read the unlock code directly from the firmware. In case of Android handsets, the bootloader of the device can be unlocked to flash a new CID number(11111111, which indicates an unlocked device) and hence the SIM Lock is effectively removed.
Most handsets have security measures built into their firmware that protects them from repeated attempts to guess the unlock code. After entering more than a certain number of incorrect codes the phone becomes hard-locked and unlocking hardware must to be used in order to unlock them.
Read more about this topic: SIM Lock
Famous quotes containing the words unlocking and/or technology:
“The mark of the man of the world is absence of pretension. He does not make a speech; he takes a low business-tone, avoids all brag, is nobody, dresses plainly, promises not at all, performs much, speaks in monosyllables, hugs his fact. He calls his employment by its lowest name, and so takes from evil tongues their sharpest weapon. His conversation clings to the weather and the news, yet he allows himself to be surprised into thought, and the unlocking of his learning and philosophy.”
—Ralph Waldo Emerson (1803–1882)
“One can prove or refute anything at all with words. Soon people will perfect language technology to such an extent that they’ll be proving with mathematical precision that twice two is seven.”
—Anton Pavlovich Chekhov (1860–1904)