Patent ID: 8903361

Claim:
A network locking method for a terminal, comprising: registering a subscriber identity module (SIM) card of the terminal with a network based on an international mobile subscriber identity (IMSI) number carried on the SIM card, obtaining a public land mobile network (PLMN) number of the network; forming a valid PLMN number segment according to a first set digits of an IMSI number of at least one SIM card allowed to be used by the terminal, and storing the valid PLMN number segment on the terminal through codes; obtaining the valid PLMN number segment pre-stored on the terminal by using the plurality of first digits of the IMSI number; comparing the PLMN number of the network with the valid PLMN number segment pre-stored on the terminal and allowing or limiting, according to a comparison result, use of the SIM card by the terminal; and performing security verification on the terminal after upgrading the terminal, wherein the security verification comprises: calculating one Hash value according to multiple image files loaded on the board and forming a digital certificate according to the Hash value; signing the digital certificate by using a private key of a preset pair of public and private keys and putting the signed digital certificate into a boot image file of the board; and performing integrity verification on the digital certificate by using a public key of the preset pair of public and private keys, obtaining the Hash value in the digital certificate and comparing the Hash value with a pre-stored valid Hash value, wherein if the two are not consistent, it is determined that the board is insecure; otherwise, it is determined that the board is secure.