Tor

$53 Kills the Tor Network

(And They Won't Fix It)

Sam

Sam

— 2 min read
$53 Kills the Tor Network

Tor's directory protocol has a fundamental design flaw that costs $53 to exploit. Purdue researchers disclosed it December 2024, published the fix, and got ghosted. The vulnerability lives in the bounded synchrony assumptions target five directory authorities with basic DDoS traffic and the entire network collapses. 2 million daily users relying on infrastructure held together by hope.

The current protocol fails completely under bandwidth exhaustion attacks. The proposed partial synchrony model works even when five authorities lose connectivity, generates consensus documents in 15 minutes under 0.5mbps conditions where the existing system just dies. The implementation exists in rust, the performance benchmarks prove it works, and the Tor Project keeps running vulnerable C code while collecting six-figure salaries and major donor funding.
Arti doesn't have directory authority implementation on the roadmap. The legacy protocol keeps running with known attack vectors documented since 2022.

Academic papers keep proposing fixes, researchers keep getting ignored, and state adversaries can disable the primary anonymity network for less than dinner costs.
This covers the Purdue research paper, the specific technical failure in the directory protocol, why current DDoS mitigation doesn't address application layer design flaws, and what the fix actually requires versus what's being deployed.

  1. Purdue DDoS Paper (Main Source):
  2. Equivocation Attack Paper (Luo et al. 2024):
  3. Point Break Paper (Jansen, Vaidya, Sherr 2019):
  4. Partial Synchrony Paper (Dwork, Lynch, Stockmeyer 1988):

Tor project sources:

  1. GitLab Issue #33018 (2021 Attack):
  2. Tor Metrics:
  3. Directory Protocol Spec:
  4. DoS/Memory Exhaustion Spec:
  5. Arti Development:

ADDITIONAL SUPPORTING SOURCES:

  1. Sniper Attack Paper:
  2. Network Threat Model:
  3. Onion Service DoS Guidelines:

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