EBDL: Effective blockchain-based covert storage channel with dynamic labels

Blockchain-based covert communication has opened up a new research direction for the covert communication field. In blockchain-based storage covert communication, reliability can be guaranteed because of the inherent immutable property of blockchain. Besides, enhanced undetectability is also achieved because the sender and the receiver do not need to establish a direct connection or be online simultaneously. However, in existing blockchain-based solutions, pre-negotiated and fixed addresses are used as static labels to scan the specific transaction that embeds covert messages, which increases the risk of channel exposure. Moreover, some of them do not support large covert message transmission. In this paper, we present an effective blockchain-based covert storage channel with dynamic labels. More specifically, a novel dynamic label mechanism is proposed to help the receiver extract the covert message efficiently, whereas adversaries cannot distinguish whether a block contains specific transactions. Besides, a message segmentation mechanism is also proposed to achieve large covert message transmission. Theoretical security analysis and detailed experimental evaluations based on the public Ethereum blockchain network show that the proposed scheme is secure under Chosen Hidden-text Attacks with acceptable efficiency.