We propose and numerically demonstrate a secure key distribution scheme based on the dynamic chaos synchronization of two external cavity vertical-cavity surface-emitting lasers (VCSELs) subject to symmetric random-polarization injections. By exchanging the random parameters that control the polarization angles of the driving injection, Alice and Bob can identify the time slots in which high-quality private chaos synchronization is achieved and independently generate a shared key from the synchronized polarization difference signals of their local VCSELs. The results show that Gb/s key distribution with a low bit error ratio can be achieved, and the shared key can pass all NIST tests, which guarantee the randomness of the key. In the proposed scheme, the exchange messages do not contain any information about the key generation, which affords a high-level of security for key distribution.
A security-enhanced chaos communication scheme with time delay signature (TDS) suppression and phase-encrypted feedback light is proposed, in virtue of dual-loop feedback with independent high-speed phase modulation. We numerically investigate the property of TDS suppression in the intensity and phase space and quantitatively discuss security of the proposed system by calculating the bit error rate of eavesdroppers who try to crack the system by directly filtering the detected signal or by using a similar semiconductor laser to synchronize the link signal and extract the data. The results show that TDS embedded in the chaotic carrier can be well suppressed by properly setting the modulation frequency, which can keep the time delay a secret from the eavesdropper. Moreover, because the feedback light is encrypted, without the accurate time delay and key, the eavesdropper cannot reconstruct the symmetric operation conditions and decode the correct data.
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