A Blockchain-Based Secure Covert Communication Method via Shamir Threshold and STC Mapping

Covert communication is a crucial technology that hides information in the redundant structure of the file and transmission through public channel to achieve the secure delivery of information. The blockchain network, with the characteristics of anonymity, decentralization and tamper-proofing, can make up for the shortcomings of multimedia-based covert communication, which include the easy exposure of the identity for both parties, the vulnerability to destruction during communication and the weak robustness of the channel. Therefore, the blockchain network is an ideal channel for covert communication. Nevertheless, the existing covert communication methods face certain challenges based on blockchain, such as the lack of a secure channel for transferring the master key, low embedding capacity, and weak detection resistance. In view of this, this paper proposes a covert communication method based on Shamir threshold and STC mapping, which is suitable for public chain networks. The proposed method first decomposes the master key into sub-keys by introducing Shamir scheme, and the sub-keys are shared with the help of transaction amounts on a blockchain. Then, a mapping relation is established to ensure that the transaction amounts carrying the secret are evenly distributed. Finally, secret information is hidden in the mapping relationship and the transaction amount is interwoven, which is published to the blockchain through transactions to complete covert communication. The introduction of Shamir threshold breaks the limitation that master key cannot be safely transmitted due to the lack of a secure channel in the research of covert communication based on blockchain, thereby enhances the security of the method. Meanwhile, Shamir threshold scheme based on public chain, can solve the issue that the master key cannot be reconstructed due to dishonest participants providing invalid subkeys on traditional network. In addition, the proposed STC mapping can not only improve the detection resistance but also increase the embedding capacity. A series of experimental results illustrate that the proposed method is more resistant to detection, and the embedding efficiency is enhanced by 27.56 times compared with existing public chain-based covert communication methods, effectively reducing the number of transactions and saving resource consumption.