Section: 4.4 NAS security 4.4.1 General
Content: This clause describes the principles for the handling of EPS security contexts in the UE and in the MME and the procedures used for the security protection of EPS NAS messages between UE and MME. Security protection involves integrity protection and ciphering of the EMM and ESM NAS messages. The signalling procedures for the control of NAS security are part of the EMM protocol and are described in detail in clause 5. NOTE: The use of ciphering in a network is an operator option. In this clause, for the ease of description, it is assumed that ciphering is used, unless explicitly indicated otherwise. Operation of a network without ciphering is achieved by configuring the MME so that it always selects the "null ciphering algorithm", EEA0.