Hi all,
We are investigating how Tor protects itself against Denial-of-Service (DoS) attacks. So far, it has been difficult to find a comprehensive top-level design document for the DoS subsystem (e.g., a torspec or proposal) that reflects the decisions that lead to the subsystem in its current form.
Specifically, we are looking at the DoS mitigation subsystem code for entry guards at src/core/or/dos.{h,c} [1]. We are trying to understand the chosen countermeasures and how the default and current consensus values came to be, e.g., the decision to limit to 3 circuits per second after the initial burst.
1) Could you kindly point us in the right direction if any such document exists?
2) If it does not exist, would you mind briefly explaining how the DoS threshold values (such as DoSCircuitCreationMinConnections, DoSCircuitCreationRate, DoSCircuitCreationBurst, and DoSConnectionMaxConcurrentCount) were chosen?
Thank you very much in advance.
Kind regards
Lennart Oldenburg KU Leuven
[1] https://gitweb.torproject.org/tor.git/tree/src/core/or/dos.c