Vergoossen Tom, Bedington Robert, Grieve James A, Ling Alexander
Centre for Quantum Technologies, National University of Singapore, Singapore 117543, Singapore.
Department of Physics, National University of Singapore, Singapore 117543, Singapore.
Entropy (Basel). 2019 Apr 10;21(4):387. doi: 10.3390/e21040387.
An application of quantum communications is the transmission of qubits to create shared symmetric encryption keys in a process called quantum key distribution (QKD). Contrary to public-private key encryption, symmetric encryption is considered safe from (quantum) computing attacks, i.e. it provides forward security and is thus attractive for secure communications. In this paper we argue that for free-space quantum communications, especially with satellites, if one assumes that man-in-the-middle attacks can be detected by classical channel monitoring techniques, simplified quantum communications protocols and hardware systems can be implemented that offer improved key rates. We term these protocols photon key distribution (PKD) to differentiate them from the standard QKD protocols. We identify three types of photon sources and calculate asymptotic secret key rates for PKD protocols and compare them to their QKD counterparts. PKD protocols use only one measurement basis which we show roughly doubles the key rates. Furthermore, with the relaxed security assumptions one can establish keys at very high losses, in contrast to QKD where at the same losses privacy amplification would make key generation impossible.
量子通信的一个应用是在一种称为量子密钥分发（QKD）的过程中传输量子比特以创建共享对称加密密钥。与公私钥加密相反，对称加密被认为对（量子）计算攻击是安全的，即它提供前向安全性，因此对安全通信具有吸引力。在本文中，我们认为对于自由空间量子通信，特别是与卫星的通信，如果假设中间人攻击可以通过经典信道监测技术检测到，那么可以实现简化的量子通信协议和硬件系统，从而提高密钥生成率。我们将这些协议称为光子密钥分发（PKD），以将它们与标准的QKD协议区分开来。我们确定了三种类型的光子源，并计算了PKD协议的渐近秘密密钥率，并将它们与其QKD对应物进行比较。PKD协议仅使用一种测量基，我们表明这大约会使密钥率翻倍。此外，由于安全假设较为宽松，与QKD在相同损耗下隐私放大将使密钥生成变得不可能相反，人们可以在非常高的损耗下建立密钥。
