# A Hybrid Encryption Scheme for Quantum Secure Video Conferencing Combined with Blockchain
## 2 Preliminaries
### Quantum Key Distribution
\begin{table}
\begin{tabular}{c c} \hline \hline
**Notations** & **Definitions** \\ \hline \(F\) & Quantum key file \\ \(ck\) & Classic binary key \\ \(qk_{BA}\) & [PERSON] [PERSON]’s symmetric binary quantum key \\ \(l_{l}\) & Row \(i\) of the database \\ \(QT\) & Quantum key table \\ \(QT_{B}^{l}\) & Row \(l\) in Table \(B\) \\ \(M_{i}\) & Group \(i\) plaintext with a length of 1024 Byte \\ \(C_{i}\) & Group \(i\) ciphertext with a length of 1024 Byte \\ \(Ent_{opt}(ak,M)\) & Encryption operation, where \(opt\) is the encryption algorithm \\ \(De_{opt}(qk,C)\) & Decryption operation, where \(opt\) is the decryption algorithm \\ \(ID_{AES}\) & Quantum key ID when starting AES encryption \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Notations used in our scheme. and permuted the image data to realize the encryption of images. Reference [22] obtained the quantum key according to the BB84 protocol, then fused the quantum key with the logistic chaotic sequence to generate the final key stream and permuted the image pixel values by the heteroskedastic operation to realize the image encryption. The literature [21; 22] used the basic protocol of the quantum key distribution to generate quantum keys and implemented image encryption experimentally, but did not consider the relationship between the key consumption of the one-time pad algorithm and the key generation rate based on the BB84 protocol in the actual quantum key distribution network and the influence of other related factors on image encryption. References [23; 24; 25; 26] used the quantum random walk technique to generate quantum keys and then encrypted the image information. Reference [27] fused quantum keys to chaotic sequences by nonlinear operations and used hybrid keys to encrypt images. This scheme fuses random keys with pseudo-random keys, which improves the randomness and consistency of pseudo-random keys, but reduces the randomness of quantum keys. Reference [28] proposed an image encryption scheme based on discrete-time alternating quantum walk (AQW) and the advanced encryption standard (AES), which used quantum walk technology to provide theoretically safe keys for the AES algorithm. Although References [23; 24; 25; 26; 28] used quantum random walk technique to generate quantum keys and provided a scheme for encrypting images, the quantum keys are not theoretically completely random, but have pseudo-randomness, which is different from the quantum keys generated through the quantum key distribution technique. At the same time, the generation of quantum keys is real-time, and the use of a single encryption scheme will result in the waste or tightness of quantum keys. In general, there are some image encryption schemes that introduce quantum keys, and each has its own differences, but such schemes are still relatively few. [PERSON] [29] introduced the quantum blockchain [30], proposed a new quantum blockchain scheme based on quantum entanglement, and analyzed the security of the transaction from the keys and quantum coins. [PERSON] [31] used quantum keys to encrypt bidders' private data and submit them to the blockchain and designed a quantum-based auction system on the blockchain. These schemes give the combination of quantum communication technology and blockchain; for the security proof, however, no specific experimental verification and analysis have been designed. In this paper, QKD technology is introduced into the existing video conference system scheme, making full use of the physical properties of quantum keys and combining with existing schemes to effectively strengthen the system security.