Security verification for continuous variable quantum key distribution

Noise estimate is crucial to the continuous variable quantum key distribution. In the estimate many parameters should be evaluated, including the mean, variance, attenuation and the normality. Then how the inaccuracies of so many parameters affect the security becomes a problem. Here we will discuss a test method and illustrate the relationship between its inaccuracy and the amount of secret keys. Through analyzing Eve's possible attack way of obtaining additional information, we show which parameter is determinant under specific conditions. Finally, we will see that the minimum sample size for the channel test should be exponentially proportional to the transmission distance