Practical Security Analysis Of Reference Frame Independent Quantum Key Distribution

Quantum key distribution(QKD)theoretically allows two legitimate parties to share the common secret keys.Reference Frame Independent QKD(RFI-QKD)can generate secret keys with the drift of reference frames.It has an important application prospect in earth-to-satellite,network and chip-to-chip QKD.At present,domestic and foreign researchers mainly study protocol design and experimental implementation of RFI-QKD,but the pratical security of RFI-QKD has not been research completely.In this paper,we focus on the practical security of RFI-QKD with imperfect single photon source,intensity fluctuations,finite-key and untrusted source.The main work is summarized as follows:1.Practical security analysis of passive decoy-state RFI-QKD with Heralded Single Photon Source(HSPS).HSPS has the higher single photon probability and lower vacuum state probability than Weak Coherent Pulses(WCP)source.In this paper,we propose a passive decoy-state RFI-QKD protocol with HSPS.We present formulae of the bit error rate under different bases in triggered pulse and nontrigeered pulse.And we show how to calculate the parameter C and the information of Eve.Finally,we present the formula of the secret key rate of this protocol.The results of the numerical simulation show that by combining the HSPS and the practical passive decoy-state method together,one not only can strengthen the secure transmission distance of RFI-QKD,but also can improve the secret key rate of RFI-QKD.2.Practical security analysis of RFI-QKD in the finite-key regime and intensity fluctuations regime.The statistical fluctuation of parameter estimation caused by the finite-key is an important factor to analyze the practical security in practical QKD system.In this paper,we present how to characterize the statistical fluctuations of parameters in the parameter estimation based on Hoeffding inequality and Chernoff bound.And we show how to calculate the bit error rate under different bases,the parameter C and the information of Eve.Based on the composable security definition,we present the formula of the secret key rate of RFI-QKD in the finite-key regime.Considering the intensity fluctuations,we present how to characterize the statistical fluctuations of parameters in the parameter estimation based on Azuma’s inequality.And we analyze the practical security of RFI-QKD in the finite-key regime considering intensity fluctuations.The results of the numerical simulation show that the parameters estimated by Chernoff bound are more compact than Hoeffding inequality.And from the numerical simulation,we find that the intensity fluctuation has a significant influence on the secret key rate and the secure transmission distance of RFI-QKD.The smaller key size and the larger deviation of the reference frames are,the more obvious the influence of intensity fluctuation will be.3.Practical security analysis of RFI-QKD with an untrusted source.In this paper,we present the RFI-QKD with an untrusted source based on the “plug&play” structure and present the practical security analysis of this protocol.We can get the photon number information of the untagged pulse in the sample pulse by intensity monitor.With this information,we present how to calculate the upper bound of bit error rate of the single photon in different bases,the parameter C and the information of Eve in untagged pulse.Considering the finite-key effect,we present how to characterize the statistical fluctuations of parameters in the parameter estimation based on Chernoff bound.The results of the numerical simulation show that RFI-QKD with an untrusted source can also generate secret keys with the drift of reference frames.