Cryptographically secure radios based on directional modulation

Directional modulation (DM) can be regarded as a new frontier in physical layer communication security. This new technique uses an antenna array as a spatial encryption system which partitions the surrounding space into regions where the transmission is either perfectly intelligible or intentionally obfuscated. Still, energy and spectral efficiencies of current DM systems as well as their cryptographic robustness lag behind the modern performance standards in cryptography and radio-communication. This contribution proposes a generalization of the DM concept which overcomes the limitations of its initial formulation by making it both compatible with state-of-art digital modulations and cryptographically secure. Numerical analyses as well as real-world, high bit-rate implementation results are presented in support of the proposed approach.