Onions Got Puzzled: On the Challenges of Mitigating Denial-of-Service...
summary
Researchers demonstrate OnionFlation, a family of attacks that sends a few hundred low-volume requests at the end of each 5‑minute measurement window (an end-rush), tricking Tor’s puzzle difficulty updater into skyrocketing difficulty and causing about half of clients to time out after 90 seconds. The attack costs only a couple of dollars per hour on the live Tor network. A tunable difficulty-update parameter is built and evaluated: it reduces inflation impact while keeping classic DoS resistance with only a few seconds of added delay.
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chapters (7)
- 0:00Onion services and DoS challenges
- 2:01Standard DoS mitigations fail
- 3:28Proof of Work puzzles mitigation
- 4:10Onion inflation attack
- 5:56Difficulty update algorithm exploited
- 8:50Tunable mitigation design
- 10:35Summary and future
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