Research On Coupling Encryption Of The EDF Laser Based On Real Random Sequence And Neural Code

Random sequence can be divided into true random sequence and pseudo random sequence. Both sequences can be used in the field of encryption as passwords. But a pseudo random sequence is generated by algorithm. However good an algorithm is, it will make a pseudo random sequence periodic and cannot guarantee the safety of password system. A true random sequence, however, is derived from the real physical world. It can truly realize “one password at a time” and is thus most reliable source of password system. However, the generation of true random sequence must involve a physical process, which is relatively difficult. The subsequent processing is complex,so the application and development are limited to a certain extent.There are many ways to generate a true random sequence. They can be roughly divided into two types. One doesn't depend on mathematical model, such as noise of electrical equipment, frequency jitter, mouse track, single photon emission, etc. The other depends on mathematical model, for example, chaos produced by optical system.A random sequence independent of mathematical model generally has no obvious characteristic, whereas a random sequence dependent on mathematical model generally has some characteristics, such as chaotic or hyperchaotic. These chaotic or hyperchaotic sequences are more advantageous when applied to encryption system.At present, chaotic or hyperchaotic sequences generated by optical system are most suitable for the field of encryption. To get stable system output, all existing experiments adopt all-optical devices. But all-optical devices are costly and their realization is complex. It will increase the difficulty of preliminary experiment to use all-optical system simply to get a random sequence. So how to use an optical system model, without using an optical device to generate true random sequence has become an imminent problem.This paper adopts a physical method to generate true random sequence. The template is an erbium-doped fiber laser dynamic system. For the work in this paper,the following innovations are proposed:1. An analog circuit is designed to realize the output of true random sequence of single-ring erbium-doped fiber laser. Devices, such as resistor, capacitor and operational amplifier are used to calculate according to the requirements of dynamic equation and finally realize its operational function. It casts light upon the design of other realizable mathematical models with a delay item.2. By adding a delay item, the single-ring erbium-doped fiber laser is improved,to make the system more complex, random and unpredictable and output hyperchaotic sequence successfully. The improved deformation system has a complex structure, so it can only generate pseudo random sequence at the present stage.3. Based on a double-ring erbium-doped fiber laser model, an analog circuit is designed, to cast light upon the design of high-dimensional hyperchaotic system.4. It has been proposed for the first time that true random sequence coupled with tree parity machine neural network can generate key streams for the purpose of encryption. The key streams are applied to image encryption and achieved good effect.