title: Eavesdropping in chaotic optical communication using the feedback length of an external-cavity laser as a key.
abstract: An external-cavity laser (ECL) operating in a chaotic state is usually used in a chaotic optical secure communication system and its feedback length (FL) is often regarded as an additional key. Our analyses show that an eavesdropper's (Eve) laser can synchronize with a transmitter (Alice) without any knowledge of the FL by simply increasing the injection strength. A sequence of a 1 Gbit/s nonreturn-to-zero message encoded by the FL as the key is successfully eavesdropped. The reason for the synchronization deviation between Alice's and Eve's lasers is given. Our results indicate that the FL as a key cannot enhance the security of chaotic optical communication using long-ECLs.
authors: Department of Physics, College of Science, Taiyuan University of Technology, Taiyuan 030024, China.
authors: Qingchun
authors: Q
authors: Zhao
authors: Yuncai
authors: Y
authors: Wang
authors: Anbang
authors: A
authors: Wang