First, we need to understand the basic structure of a SIM card. SIM card is the abbreviation of (Subscriber Identity Module), also known as user identification card, smart card, GSM digital mobile phone must be installed with this card to use. It stores digital mobile phone customer information, encrypted keys and user phone books on a computer chip, which can be used to identify GSM network customer identities and encrypt the voice information of customers during calls.
A SIM card is a chip with a microprocessor, which contains 5 modules, each corresponding to a function:
CPU (8-bit/16-bit/32-bit), program memory ROM, working memory RAM, data memory EEPROM and serial communication unit, these five modules are integrated in a single integrated circuit.
When connecting a SIM card to a mobile phone, a minimum of 5 cables are required: * Power (Vcc) * Clock (CLK) * Data I/O port (Data) * Reset (RST) * Ground (GND)
In the original post, Lz pasted the pins with transparent glue [RST], and SIM-RESET is responsible for the working reset signal of the SIM card, which is used to reset the internal processor of the SIM card.
Perhaps seeing this, you still can't understand why blocking the SIM-RESET pin can save traffic and phone bills. In fact, this has something to do with the SIM card verification process. The SIM card verification process is divided into the following steps:
1. The mobile phone sends a network access request to the network
2. A random string of reply on the network
3. The phone receives and gives it to the SIM card,
4. The card is calculated according to the algorithm in the photo, and the result is returned to the mobile phone
5. The mobile phone sends its calculation results, IMEI, and ICCID back to the network, and the network reads the ICCID to analyze whether it is a local number.
6. The network returns legal information, and the KC code is issued to complete the network access process
The SIM-RESET pin is blocked, and the internal processor of the SIM card cannot be reset, that is to say, when the mobile phone sends a network access request to the network, receives the string and processes the string, because the SIM-RESET pin is blocked, the calculated result is different from the original structure. The mobile phone feeds back this "wrong legal information" to the operator, and the operator returns the corresponding "legal information" and "KC code", and completes the network access process.
Because the above authentication process is only the authentication process of 2G network, the authentication process of 3G network is different and much more complicated. So the original post Lz told everyone that you need to set the access point to wap. This is also the reason why some sealing glazes fail to succeed, as long as the access point is set to wap.
Some sealing glazes may ask why this still takes a small amount of traffic, such as the original title "Only 0.87KB was used on the first day, almost no traffic was needed, and only 10KB was used to play games on the second day". This is because during the authentication process, the traffic sent by the mobile phone to the network to the network is counted in the original SIM card (that is, the SIM you are using), and the traffic used after authentication is calculated on a SIM card that does not exist because the SIM-RESET pin is blocked and the wrong string is calculated.
The 4G card adopts new technology and algorithm for two-way encryption and decryption verification, because the "wrong legal information" calculated by blocking the SIM-RESET pin is fed back to the operator, and the operator will decrypt and match it.
To sum up, this is also the deep reason why operators have launched free replacement of 4G cards, and cannot exchange from 4G cards back to 3G cards. |
Posted on 11/8/2014 6:40:30 PM
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