# A Hybrid Encryption Scheme for Quantum Secure Video Conferencing Combined with Blockchain
## 2 Preliminaries
### Quantum Key Distribution  
The quantum key distribution (QKD) can enable both parties of the communication to generate and share a random and secure key to encrypt and decrypt the communication message based on quantum mechanical properties. QKD protocols mainly comprise the single-photon-based QKD protocol, the continuous variable-based QKD protocol, and the quantum-entanglement-based QKD protocol, wherein the BB84 protocol [13] is a more common protocol used in current research. The BB84 protocol, also known as the four-state protocol, was proposed by [PERSON] and [PERSON] in 1984. The implementation of this protocol requires two channels: one is a classic channel and the other is a quantum channel for transmitting the quantum state carrying random numbers. In the protocol, the quantum state corresponds to the classical binary code, wherein the \(0^{\circ}\) or \(45^{\circ}\) phase corresponds to the classical bit \(0\) and the \(90^{\circ}\) or \(-45^{\circ}\) phase corresponds to the classical bit \(1\). Use the \(|\psi_{00}\rangle\) and \(0^{\circ}\) phase quantum state of the corresponding photon, the \(|\psi_{10}\rangle\) and \(90^{\circ}\) phase quantum state of the corresponding photon, and the \(|\psi_{11}\rangle\) and \(-45^{\circ}\) phase quantum state of the corresponding photon. The basic principle is that [PERSON] sends the single photon of horizontally vertical and positive and negative quantum states to [PERSON], and [PERSON] measures the quantum state. After receiving all the information sent by [PERSON], [PERSON] performs the base loss comparison with [PERSON] through the classic channel; if the base loss is the same, the original quantum key is obtained. Since [PERSON] cannot observe the photon phase quantum state without changing the state, once it is eavesdropped, the bit error rate will be significantly improved. Therefore, the key distribution security can be guaranteed in theory, thus providing a safe channel that is difficult to crack for information transmission. In addition, it can effectively deal with security threats such as channel eavesdropping and high-performance computational attacks, therefore greatly improving the encrypted communication security and ensuring the network transmission security. At present, the construction of actual quantum networks such as quantum satellite networks, quantum metropolitan area networks, and quantum trunk networks [14], the participation of Alibaba Cloud, mobile, and telecom operators, and the integration of quantum keys and classical applications have involved many fields. QKD was used for secure data transmission in network microgrids [15]. A satellite-based QKD network was created to realize the quantum key distribution between two legitimate users and the satellite for secure communication [16]. [PERSON] [17; 18; 19] introduced the combination scheme of the quantum key and power business and gave the security protection architecture of a new urban power business. The integration of quantum keys with classical applications has been involved in several fields, but in the existing schemes, most of them consider the scheme of using quantum keys and never consider the monitoring of the operation status of quantum key distribution networks. In video image encryption, [PERSON] [20] first proposed an image encryption algorithm based on quantum cryptography. [PERSON] [21] used a six-state scheme to generate quantum keys, performed a XOR operation with the image data,