Patent ID: 9681292
Date: 2017-06-13
CPC Classifications: H04L,H04W,Y04S

Claim:
1. A method for handling, ciphering keys in a mobile station comprising a mobile equipment (ME) and a Universal Subscriber Identity Module (USIM), the method comprising: obtaining, by a processing circuit, a Universal Mobile Telecommunications System (UMTS) cipher key (CK), a UMTS integrity key (IK), and a UMTS ciphering key sequence number (CKSN) from the USIM; generating, by the processing circuit, a 128-bit ciphering key (Kc-128) from the UMTS CK and the UMTS IK; storing, by the processing circuit, the Kc-128 and the UMTS CKSN on the mobile equipment, separate from the USIM, wherein the stored UMTS CKSN is associated with the stored Kc-128; determining, by the processing circuit, that a ciphering algorithm requiring a 128-bit ciphering key is to be taken into use for operation in one of a packet-switched domain and a circuit-switched domain; prior to applying the stored Kc-128 to the ciphering algorithm, verifying a validity of the stored Kc-128 by: applying, by the processing circuit, the stored Kc-128 to the ciphering algorithm responsive to verifying the validity of the Kc-128.