Secure Key Generation and Distribution Scheme Based on Signal Hiding and Concatenated Coding in Optical Fiber

A key generation and distribution scheme in coherent optical system is proposed, which is compatible with the current fiber infrastructure. The random key is generated by quantifying system noise which is obtained according to the training sequence. The key signal with the low power is hidden in the 2¹² × 2¹² TQAM signal. The legal party can extract the key signal from 16 QAM signals, but the attacker can only extract the key signal from 212 × 212 TQAM signals. Compared with processing 212 × 212 TQAM signals, existing algorithms are more effective at processing 16 QAM signals. It provides the security of key distribution and is verified by experiment. The concatenated coding including LDPC coding and differential coding is employed to get error-free key and expand the security space. Since differential coding leads to cumulative errors, the key error rate is ∼50% when the key error rate is above the LDPC threshold. The proposed scheme achieves an error-free key with KDR of 2.5 Gbps over 80 km SSMF, which does not require the presetting, external random source, and additional device.