Section: 4.7.1.2a.2 Integrity checking of GMM signalling messages in the MS
Content: Except the messages listed below, no GMM signalling messages shall be processed by the receiving GMM entity in the MS or forwarded to the SM entity, unless the use of integrity protection has been successfully negotiated: - GMM messages: - IDENTITY REQUEST (only if the requested identification parameter is IMSI) - ATTACH REJECT (if the cause is not #25) - AUTHENTICATION AND CIPHERING REJECT - ROUTING AREA UPDATE REJECT (if the cause is not #25) - DETACH ACCEPT (for non power-off) NOTE: These messages are accepted by the MS without integrity protection, as in certain situations they are sent by the network before integrity protection can be activated. All SM messages shall be integrity protected. Once the integrity protection has been successfully negotiated, the receiving GMM or SM entity in the MS shall not process any GMM signalling messages unless they have been successfully integrity checked by the LLC layer. If GMM signalling messages, having not successfully passed the integrity check, are received, then the LLC layer in the MS discards that message. The processing of the AUTHENTICATION AND CIPHERING REQUEST message, at authentication, that has not successfully passed the integrity check at GMM layer is specified in subclause 4.7.7.2. If any GMM or SM signalling message is received without integrity protection even though integrity protection has been successfully negotiated, then the GMM layer shall discard this message.