A wireless transmit/receive unit (WTRU) includes a control plane (C-plane) packet data convergence protocol (C-PDCP) layer which performs ciphering of a signaling message. The C-PDCP layer is activated upon power up of the WTRU and initial security parameters are loaded to the C-PDCP layer. An initial connection signaling message and a user identity are ciphered using the initial security parameters even before the WTRU is authenticated. The initial security parameters including a ciphering key (CK) may be generated from system information broadcast from the network. The CK may be a public key for asymmetric encryption, and may be selected from a public key set broadcast by or derived from the network system information. An index of the selected public key may be separately encoded. Alternatively, the index may be communicated by using a Diffie-Hellman key exchange method.