CDMA Physical Layer Built-in Security Enhancement

Served as one of the most widely used wireless airlink interface, CDMA has been identified as a major technique for 3G wireless communications. The current IS-95 CDMA provides a near-satisfactory security solution to voice centric wireless communications, since generally each voice conversation only lasts a very short period of time. However, the security features provided by IS-95 CDMA are far from adequate and being acceptable when used for data communications. In this paper, the security weakness of the existing CDMA airlink interface is analyzed. Encrypted key stream based on advanced encryption standard (AES) is proposed to be used in the scrambling process, instead of using the scrambling sequence generated from the 42bit linear feedback shift register (LFSR) as in IS-95. Ensured by AES, physical layer built-in security of the proposed scheme is much stronger than that of the IS-95 system.