Secure Key Generation and Distribution at Physical Layer by Using Ultra-Long Fiber Laser

Secure fiber-optic communication systems are an important area of research and development in the IT industry. In this work, we report the development of a promising fiber laser system for physical-layer secure key generation and distribution. This is a pulsed ultra-long Erbium fiber laser in which pulse shaping is symmetrically split between two communicating parties (Alice and Bob). The proposed protocol for the physical-layer secure key generation and distribution is based on control of the duration of generated laser pulses. Alice and Bob contribute random binary values to the secure key generation by making independent choices of their states in the split pulse shaping every bit cycle. The key exchange is secured whenever different choices lead to the same pulse duration, thereby confusing an eavesdropper (Eve). Two strong algorithms for the transmitted data encryption at the physical layer are proposed and discussed as well. One of them uses a private key to encrypt the message entered by one of the communicating parties, and the other uses a meaningful message entered synchronously by the other party.