We propose and demonstrate a high-speed physical-layer key distribution in fiber networks using synchronization of polarization states. An error-free and true random key generation rate of 2 Gb/s is achieved over 20 km single-mode fiber.
A physical-layer secure key generation and distribution (SKGD) scheme in classical fiber channel is proposed and demonstrated using a bidirectional wide-band polarization scrambler (WBPS), to alter rapidly and symmetrically the state of polarization (SOP) for the two counter-propagating optical signals in fiber. Due to the optical channel reciprocity, highly-consistent key bits can be extracted from the correlated SOP fluctuations, while the key secrecy is ensured by the fiber channel uniqueness. A final key generation rate (KGR) of 2.7 Gb/s is demonstrated over 10 km single mode fiber (SMF), where error-free and true randomness of the generated key are achieved after post-processing. The obtained KGR at Gb/s makes a further step towards the implementation of one-time-pad data encryption with perfect secrecy in fiber networks.
High-speed physical-layer secure key generation and distribution (SKGD) schemes via channel reciprocity are achieved using external electro-optical modulation or random source distribution via additional fiber links. Here, we propose and demonstrate an SKGD scheme using the fluctuation of polarization states from an amplified spontaneous emission (ASE) source, without any external electro-optical modulation or additional fiber link. Experimentally, an error-free key generation rate (KGR) of 10.1 Gb/s is achieved over a 10-km standard single-mode fiber (SSMF), with true randomness originating from ASE. Moreover, the single fiber channel can be shared for SKGD as well as data transmission, allowing the integration of the proposed SKGD with the deployed fiber infrastructure.
Dynamic properties of optical signals in fiber channel provide a unique, random and reciprocal source for physical-layer secure key generation and distribution (SKGD). In this paper, an inherent physical-layer SKGD scheme is proposed and demonstrated, where the random source is originated from the dynamic fluctuation of the instant state of polarization (SOP) of optical signals in fiber. Due to the channel reciprocity, highly-correlated fluctuation of Stokes parameter of SOP is shared between the legal partners, where an error-free key generation rate (KGR) of 196-bit/s is successfully demonstrated over 25-km standard single-mode fiber (SSMF). In addition, an active polarization scrambler is deployed in fiber to increase the KGR, where an error-free KGR of 200-kbit/s is achieved.
Key distribution is a major challenge of secure communication. Computational approaches to key distribution are breached by quantum algorithms, while quantum key distribution (QKD) is an expensive, slow, and sophisticated solution. Secure key generation and distribution from unpredictable and inherent physical-layer properties of optical fiber channel is a classical, simple and cost-effective solution. However, the quasi-static nature of fiber channels dramatically limits the available key generation rate (KGR) to the order of ~kbit/s. Here we effectively accelerate the KGR by six orders of magnitude using a developed high-speed chaotic polarization scrambler (CPS) driven by digital chaos in fiber channels. An error-free KGR of 284.8 Mbit/s is experimentally demonstrated over a 24 km standard single-mode fiber (SSMF), where the generated key passes the random test suite. Moreover, we fully analyze the security mechanism and find that a strong asymmetry exists between legal and illegal users, ensuring a high-level of security against potential fiber-tapping attacks. This scheme provides a major step towards the practical implementation of the “one-time-pad” in secure data transmission over fiber networks.