Section: 5.1.3 Confidentiality
Content: The following security features are provided with respect to confidentiality of data on the network access link: - cipher algorithm agreement: the property that the MS and the SN can securely negotiate the algorithm that they shall use subsequently; - cipher key agreement: the property that the MS and the SN agree on a cipher key that they may use subsequently; - confidentiality of user data: the property that user data cannot be overheard on the radio access interface; - confidentiality of signalling data: the property that signalling data cannot be overheard on the radio access interface; Cipher key agreement is realised in the course of the execution of the mechanism for authentication and key agreement (see 6.3). Cipher algorithm agreement is realised by means of a mechanism for security mode negotiation between the user and the network (see 6.4.5). This mechanism also enables the selected ciphering algorithm and the agreed cipher key to be applied in the way described in 6.6.