Method and system for determining that a SIM and a SIP client are co-located in the same mobile equipment

A method for determining that a SIM and a SIP client are co-located in the same mobile equipment, ME,

• wherein a SIP server, a SIP Location Register, SLR, and the ME are communicatively interconnected, the SIM being arranged in the ME, the SIM having an IMSI,
• the method comprising the following steps performed by a security module, SLM-SM, included in SIM:
• encrypting, using a key, a variable derived from the IMSI,
• providing a first password parameter as a result of the encrypting step;
• and
• calculating an ME security code by XOR operation of the password parameter and an identity of the ME;
• the method further comprising the following steps performed by a SIP client location manager, SLM, included in the ME:
• receiving the ME security code;
• performing an XOR operation of the ME security code and the identity of the ME, and
• providing a second password parameter as a result of the XOR operation;
• the method further comprising a process, performed by the SLR, for SIP client presence and location update for mobile operators MSISDN, the process including:
• receiving the second password parameter from the SLM via the SIP server;
• decrypting the second password parameter using the key;
• performing an XOR-operation of the decrypting result with a seed;
• comparing the result of the XOR-operation with the IMSI;
• and
• upon match, determining that the SIM and the SIP client are co-located in the same ME.