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ABC-Channel: An Advanced Blockchain-based Covert Channel

Xiaobo Ma, Pengyu Pan, Jianfeng Li, Wei Wang, Weizhi Meng, Xiaohong Guan

TL;DR

ABC-Channel tackles secure, high-throughput covert communication over public blockchains by combining off-chain contactless negotiation, GAN-based indistinguishable transaction feature masquerading, and dynamic address-based untraceable identities. The approach uses kleptography and subliminal channels to synchronize keys and embed messages, with ECDH-derived chaincode enabling a shared Esk_{AB} without exposing negotiation data. A Bitcoin testnet prototype demonstrates substantial concealment and competitive transmission efficiency, achieving up to $256$-bit messages per covert transaction and approximately $347$ bits per $Tx_c$ on average, with costs around $3589$ Satoshi per $Tx_c$. The work provides a platform-agnostic blueprint for blockchain covert channels and informs defenses against on-chain analysis and off-chain de-anonymization threats.

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.

ABC-Channel: An Advanced Blockchain-based Covert Channel

TL;DR

ABC-Channel tackles secure, high-throughput covert communication over public blockchains by combining off-chain contactless negotiation, GAN-based indistinguishable transaction feature masquerading, and dynamic address-based untraceable identities. The approach uses kleptography and subliminal channels to synchronize keys and embed messages, with ECDH-derived chaincode enabling a shared Esk_{AB} without exposing negotiation data. A Bitcoin testnet prototype demonstrates substantial concealment and competitive transmission efficiency, achieving up to -bit messages per covert transaction and approximately bits per on average, with costs around Satoshi per . The work provides a platform-agnostic blueprint for blockchain covert channels and informs defenses against on-chain analysis and off-chain de-anonymization threats.

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.
Paper Structure (19 sections, 4 equations, 3 figures, 8 tables, 4 algorithms)

This paper contains 19 sections, 4 equations, 3 figures, 8 tables, 4 algorithms.

Table of Contents

  1. Introduction
  2. Background And Threat Model
  3. Background
  4. Threat Model
  5. System Design
  6. System Overview
  7. Contactless Channel Negotiation
  8. Indistinguishable Transaction Feature
  9. Untraceable Communication Identity
  10. Evaluation
  11. System Implementation
  12. Data Collection
  13. Black-box Testing
  14. White-box Testing
  15. Impact of Transaction Parameters on Concealment
  16. ...and 4 more sections

Figures (3)

  • Figure 1: Blockchain-based covert channel threat model.
  • Figure 2: ABC-Channel architecture.
  • Figure 3: Parameter generation (Italics: generated using our method).