Shared security context

Creation or update of a security context between user equipment and MSC/VLR (Mobile Switching Center/Visitor Location Register) for circuit switched domain services is provided. The creation or update is based on conversion of the security context used in an evolved Universal Terrestrial Radio Access Network (E-UTRAN) in the Mobility Management Entity (MME) to a security context for the circuit switched domain target system and transferring it to a MSC/VLR. When user equipment is moved from E-UTRAN to GSM EDGE Radio Access Network/Universal Terrestrial Radio Access Network (GERAN/UTRAN), a MME does not need to perform authentication and key agreement procedures to establish shared circuit switched security context for the user equipment.