源自:ITU-T标准中的密钥管理相关（Key management）

Alternative scheme of key relay

A key relay scheme to share a key between the originating node and destinating node is illustrated in Figure 3. The Key_AB is generated between KMA-A and KMA-B. The Key_AB is relayed from KMA-B to KMA-C by OTP encryption with the Key_BC. It is relayed from KMA-C to KMA-D by OTP encryption with Key_CD and finally supplied to KSA-D. 

Figure 3 - Scheme of key relaying from point to point in Recommendation draft ITU-T Y.3800 (case 1) 

In case 2 which is illustrated in Figure 4, a random bit string Key_RN which is generated locally at KMA-A is used for key relay from KMA-A to KMA-D.

Figure 4 - Scheme of key relaying from point to point in Recommendation draft ITU-T Y.3800 (case 2)

There are two problems for the schemes case 1 and case 2 of key relaying from point to point in real application. One is that the XOR ciphertext key and the corresponding decryption key may coexist on one relay node, which has a security risk. The other is that the network has complex KMA links between nodes, which results in implementation difficulty. To help alleviate the above problems, two modified schemes of key relaying will be described in the following.

QKD网络的中继方案

原文：https://www.cnblogs.com/Limer98/p/12590983.html