Prof. Dr.-Ing. Werner Henkel, Dr. Mathias Bode
Physical-layer security in wireless communication is a challenging topic needed to allow for secure and reliable information transfer, otherwise subject to eavesdropping. In particular, physical-layer key generation methods use the properties of the channel itself to generate keys that are only shared by legitimate users, the ones experiencing the same channel. Having this in mind, we study different methods that enhance and support the security at the physical-layer.
Firstly, a stationary, reciprocal channel is considered and reconfigurable aperture antennas (RECAP) are used to randomize it such that a frequent key generation process is ensured. The physical-layer key generation process is then modeled as a vector quantization operation and a key reconciliation approach based on Slepian-Wolf coding and LDPC codes is implemented to correct possible key differences. A linear programming technique based on a rate maximization criterion is employed to obtain the redundancy needed to protect the reconciliation bits and the optimized variable node sub-degree distributions. The performance of the final LDPC code is evaluated by simulating the bit-error ratio (BER).
Secondly, the focus is placed on blind beamforming algorithms, techniques commonly used by unauthorized receivers to gain access to the information shared by legitimate users. We investigate how fast and accurate an eavesdropper can obtain the data as a result of blind beamforming and what the requirements are to do so. Moreover, we study if and how the transmission of a jamming signal can deteriorate the quality of interception or complicate the process of blind beamforming and therefore support physical-layer security. The residual SINR at the output of the beamformers and the recovery failure rate are the two main performance indicators employed.
[Thesis] Physical-Layer Security