DLchain: A Covert Channel over Blockchain Based on Dynamic Labels

With the continuous improvement of the traffic analysis techniques, traditional network covert channels based on the TCP/IP architecture are facing many risks. Blockchain is a new kind of decentralized public network. The openness together with strong tamper resistance of the blockchain makes it become a natural platform to construct covert channel. However, the existing blockchain-based covert channels have a major drawback: the recipient identifies the transactions containing covert messages through the fixed labels, which significantly reduces the availability and concealment of the system. In this paper, we propose a new blockchain covert channel construction scheme, DLchain, which substitutes the fixed labels with dynamic labels. We design a dynamic label generation algorithm based on the statistical distribution of the real transaction data to ensure the concealment of the dynamic labels. We prove that DLchain has the features of undetectability, anti-traceability and strong robustness.