A covert channel over blockchain based on label tree without long waiting times

Blockchain, as a decentralized database, provides natural anonymity and tamper-resistance, safeguarding the identity of both parties in covert communication and preventing malicious third parties from tampering with secret messages. Compared to traditional covert communication over a network, blockchain offers a more reliable communication carrier. However, the strict order between special transactions in blockchain covert communication increases the time consumption of communication. This paper proposes a label-tree-based covert communication model, named LTCC, which uses dynamic labels with tree-like relationships to maintain the connections between special transactions. LTCC allows senders to upload transactions containing secret messages in a single pass, free from the high latency of blockchains. Even in the event of a failed transaction submission, it is possible to regenerate the transaction containing a specific label to be submitted to the blockchain, avoiding the reuse of addresses. The experimental results indicate that LTCC possesses excellent qualities such as concealment, reliability, robustness, and communication efficiency. Therefore, it can be feasibly implemented in the present-day, mainstream blockchain systems.