Privacy in Two-Laser and Three-Laser Chaos Communications

In this paper, we compare the performances of the well-known two-laser and three-laser chaos communications schemes, in terms of privacy. It is found by numerical analysis that in optimized conditions both methods are well suited for private transmission. However, while the three-laser scheme gives its optimum performance with the twin laser pair, the two-laser scheme reaches its best performance using two slightly different lasers (the optimum pair). This results in an easier device selection and in a slightly higher privacy level of the three-laser scheme. Using a twin pair with the two-laser scheme still offers a good level of privacy in most cases; however, in principle the eavesdropper has a chance to extract the message, by selecting a suitable laser.