关键词: 网络编码, 对角矩阵, 多级网络编码, k-安全

Abstract: The current secure network coding has two methods.They are information-theoretic security and cryptography security. Among the encoding methods of information-theoretic security, the encoding scheme of the relay node uses the Random Linear Network Coding（RLNC） to generate the encoding matrix. But this method does not guarantee that the resulting matrix must be full rank and affects the decoding rate. This paper proposes a Multi-Level Network Coding（MLNC） scheme. The scheme uses the triangle matrix to encode source message. On the relay node, the node whose degree is greater than or equal to 2 is used as coding node, using multi-level network coding can make the message encode mix better. The encoding nodes generate the full rank lower triangular matrix and the full rank upper triangular matrix randomly. It uses their product as an encoding matrix. This scheme will ensure encoding matrix must be full rank. The receiving node can successfully decode the data. The result of the Matlab simulation shows that the probability of the coding matrix of MLNC satisfying k-secure can be better than RLNC. And the scheme of MLNC satisfies the theoretic security.

Key words: network coding, diagonal matrix, multi-level network coding, k-security