1. Loss of Funds
2. Privacy
3. Quality of Service

• Jamming

  • Slow
    • Proposed solution: Reputation.
  • Fast: Send a large number of HTLCs in a short time.
    • Proposed solution: Fees.
  • Mitigation has been proposed but not implemented.

• DoS Attacks

  • Implementations may not be well-prepared.
  • Not HTTP-based, so common tooling (e.g., Cloudflare) is not applicable.

• Route Hijacking

• Probing / Balance Discovery

  • Purpose: Track individual payments.
  • Becomes harder with increased traffic and noise on the network.

• Discovering Hidden Channels

• Using Tor

  • Both Lightning and Bitcoin may face disadvantages when using Tor.

• All communications in Lightning are encrypted, with onion routing for payments.
• However, these may not be sufficient.

Attack Scenario

An attacker (e.g., a large ISP or AS controller) could:

1. Correlate packets based on timing and packet size. (Revelio)
2. Infer the sender and/or receiver.

Mitigation Ideas

• Padding: Could help but raises questions about implementation:

  • Padding to a constant size vs a distribution of sizes.
  • Should mobile users have the option to opt out?

• Commitment Batching:

  • Breaks patterns and may provide some protection.
  • Challenges:
    • Attackers might adjust.
    • Only benefits large routing nodes. Except we do cover HTLCs (probes) on each individual node.

Open Questions

1. What is the contribution of timing vs message size in attacks?
2. Is a constant bitrate necessary?