Design of an OFDM Physical Layer Encryption Scheme
Abstract: This paper presents a new encryption scheme implemented at the physical layer of wireless networks employing orthogonal frequency frequency-division division multiplexing (OFDM). The new scheme obfuscates the subcarriers by randomly reserving several subcarriers for dummy data data and resequences the training symbol by a new secure sequence. Subcarrier obfuscation renders the OFDM transmission more secure and random, whereas training symbol resequencing protects the entire physical layer packet but does not affect the normal func functions of synchronization and channel estimation of legitimate users while preventing eavesdroppers from performing these functions. The security analysis shows that the system is robust to various attacks by analyzing the search space using an exhaustive key ey search. Our scheme is shown to perform better in terms of search space, key rate, and complexity in comparison with other OFDM physical layer encryption schemes. The scheme offers options for users to customize the security level and the key rate according according to the hardware resource. Its low complexity nature also makes the scheme suitable for resource-limited resource devices. Details of practical design considerations are highlighted by applying the approach to an IEEE 802.11 OFDM system case study.