Date Added: Oct 2010
Traditionally, spread-spectrum systems have been employed to provide Low Probability-of-Intercept (LPI), Low Probability-of-Detection (LPD) performance at the physical layer, but the messages transmitted over such a system are still encrypted with a powerful cipher to protect their secrecy. However, it has recently been suggested that the cryptographic security of the system can be enhanced by exploiting physical properties of Ultra-WideBand (UWB) signals. With an eavesdropper observing the communications over multipath channels between two legitimate partners sharing a secret key of a limited length, the authors consider both coherent and reference-based UWB schemes to enhance security. The security of the legitimate nodes is achieved by signal attributes based on the secret key, giving them an advantage over the adversary.