Assessing security of chaos communications against eavesdropping by pump detection

In this paper, we numerically evaluate a method which could be tried by an eavesdropper to force the standard two-laser scheme of chaos private transmission. This method is based on detection of the voltage arising across a semiconductor laser junction, and uses two lasers: one is synchronized to the transmitter (thus, reproducing chaos and rejecting the message), the other is selected and trimmed to copy the transmitter (i.e., reproducing both chaos and the message). The message is then obtained by difference and chaos cancellation. By assuming the usual parameter mismatch, which is expected to be achieved by an eavesdropper, it is shown that the method does not represent a substantial threat to the privacy of the transmission system. The scheme is also briefly considered as an alternative, but less performant, scheme for chaotic cryptography. Simulations are based on the Lang-Kobayashi model.