Section: 6.4.1 Cipher key and integrity key setting
Content: Authentication and key setting are triggered by the authentication procedure and described in 6.3. Authentication and key setting may be initiated by the network as often as the network operator wishes. Key setting can occur as soon as the identity of the mobile subscriber (i.e. P-TMSI, TMSI or IMSI) is known by the VLR/SGSN. The CK and IK are stored in the VLR/SGSN and transferred to the RNC when needed. The CK and IK for the CS domain are stored on the USIM and updated at the next authentication from this domain as specified in subclause 6.8.1.5. The CK and IK for the PS domain are stored on the USIM and updated at the next authentication from this domain as specified in subclause 6.8.1.5. If an authentication procedure is performed during a connection (PS or CS mode), the new cipher key CK and integrity key IK shall be taken in use in both the RNC and the ME as part of the security mode set-up procedure (see 6.4.5) that follows the authentication procedure.