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Research Paper on LN Payment Censorship

Research Paper on LN Payment Censorship

Original Postby cndolo

Posted on: November 5, 2024 11:57 UTC

In a recent exploration of the Lightning Network's (LN) susceptibility to censorship by network-level adversaries, such as Autonomous Systems (AS), significant findings were presented that shine a light on potential vulnerabilities within this decentralized payment system.

The research delves into how privacy attacks leverage the identifiability of peer-to-peer messages through TCP headers, despite encryption. This vulnerability is exacerbated by the centralization at the network layer, where most channels are concentrated across a few ASs, raising concerns over the ease with which application messages can be classified and subsequently manipulated.

The paper further investigates the LN's vulnerability to censorship, focusing on an attack model where a malicious AS targets only its nodes in an attempt to impose censorship without disrupting overall network operations or drawing attention to its actions. The outlined attack process involves identifying LN payment-related TCP segments, particularly update_add_htlc messages, and then selectively dropping revoke_and_ack messages to disrupt the payment process while remaining under the radar. This approach highlights the technical feasibility of such an attack due to the network's current structure and the level of control available to these centralized entities.

Moreover, the research underscores the effectiveness of implementing classification rules within XDP and netfilter programs for real-time message classification, demonstrating that such censorship is not only possible but also practically executable with existing network capabilities. However, the impact of such attacks varies greatly depending on the attacker's specific strategy and the structural characteristics of the targeted AS.

Regarding mitigation, the discussion points towards several potential countermeasures, including deviation from default ports and the use of Tor. Nevertheless, the paper argues that these solutions might be insufficient against sophisticated attackers capable of circumventing simple padding mechanisms meant to obscure message lengths. It suggests the possibility of leveraging adaptive padding techniques, like WTF-Pad, and defense frameworks such as Maybenot, to enhance resistance to censorship. Additionally, addressing the issue of network-level centralization directly, perhaps by incorporating AS information into pathfinding algorithms, emerges as another avenue worth exploring to bolster the LN's resilience against such adversarial threats.