The quantum cryptography system has been proved to unconditionally secure based on Heisenberg uncertainty principle and quantum non-cloning law. Because single-photon are not easy to be generated and detected, and based on discrete variable it is difficult for the quantum key distribution to obtain high transmission rate of information. The paper puts forward that the two parts of communication get the same initial system parameters and state of chaotic systems from initial key;it can obtain the expanded key quantity. And the security of the scheme is discussed.% 利用海森堡测不准原理和量子不可克隆定律的量子密码体制被证明是无条件安全。由于产生和检测单光子比较困难,且基于离散变量的量子密钥分配难以获得高的信息传输速率,本文介绍了利用混沌系统的特性,通过初始密钥使通信双方设置相同的系统参数和初始状态,从而获得密钥量的扩展,并讨论了方案的安全性。
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