ABC-Channel: An Advanced Blockchain-based Covert Channel

TL;DR

This paper introduces ABC-Channel, a novel blockchain-based covert communication channel that ensures contactless negotiation, indistinguishable transactions, and untraceable identities, validated through extensive testing on Bitcoin testnet.

Contribution

It presents the first full-lifecycle blockchain covert channel, addressing key challenges like contactless negotiation and untraceable identities, with a working prototype and extensive validation.

Findings

Achieves highly secure covert communication

Demonstrates state-of-the-art transmission efficiency

Validated through extensive tests on Bitcoin testnet

Abstract

Establishing efficient and robust covert channels is crucial for secure communication within insecure network environments. With its inherent benefits of decentralization and anonymization, blockchain has gained considerable attention in developing covert channels. To guarantee a highly secure covert channel, channel negotiation should be contactless before the communication, carrier transaction features must be indistinguishable from normal transactions during the communication, and communication identities must be untraceable after the communication. Such a full-lifecycle covert channel is indispensable to defend against a versatile adversary who intercepts two communicating parties comprehensively (e.g., on-chain and off-chain). Unfortunately, it has not been thoroughly investigated in the literature. We make the first effort to achieve a full-lifecycle covert channel, a novel blockchain-based covert channel named ABC-Channel. We tackle a series of challenges, such as off-chain contact dependency, increased masquerading difficulties as growing transaction volume, and time-evolving, communicable yet untraceable identities, to achieve contactless channel negotiation, indistinguishable transaction features, and untraceable communication identities, respectively. We develop a working prototype to validate ABC-Channel and conduct extensive tests on the Bitcoin testnet. The experimental results demonstrate that ABC-Channel achieves substantially secure covert capabilities. In comparison to existing methods, it also exhibits state-of-the-art transmission efficiency.