# Description Given the recent developments on Proof Of Work for Onion Services, it's [FAQ][] needs an update. [FAQ]: https://onionservices.torproject.org/technology/security/pow/ ## Tasks * [x] Update the [FAQ][] link in the [DoS guidelines page][]. Merge requested submitted at tpo/web/community!481. * [x] Add a note stating the page needs updates. Done at 793d95da98cc5b973a276b8419b2fbe80e5e1f67. * [ ] Use shorter section IDs. * [ ] Add an [admonition][] that this feature is still experimental. While we encourage operators to try it out, it may contain bugs and may not be effective under specific situations. Operators are advised to try and use the implementation that best suits their use cases, and give feedback in case of issues. * [ ] Status updates, as per discussion on 2025-08-07: * [ ] Specification updates: * [ ] [prop362: Updating the Proof-of-Work Control Loop][prop362]. * [ ] [Update Proof-of-Work Control Loop (#329)](https://gitlab.torproject.org/tpo/core/torspec/-/issues/329) (tpo/core/torspec#329). * [ ] On the Arti implementation: * [ ] Showing [the needed configuration][arti-config]. * [ ] General implementation docs at [dev/notes/service-side-pow.md](https://gitlab.torproject.org/tpo/core/arti/-/blob/main/doc/dev/notes/service-side-pow.md). * [ ] References to the [prop362][] implementation: * [ ] [Implement prop 362 (!3093) · Merge requests · The Tor Project / Core / Arti · GitLab](https://gitlab.torproject.org/tpo/core/arti/-/merge_requests/3093) * [ ] [Fix a few TODOs for PoW (!3106) · Merge requests · The Tor Project / Core / Arti · GitLab](https://gitlab.torproject.org/tpo/core/arti/-/merge_requests/3106) * [ ] [More PoW miscellania (!3132) · Merge requests · The Tor Project / Core / Arti · GitLab](https://gitlab.torproject.org/tpo/core/arti/-/merge_requests/3132) * [ ] Considering issues like the following: * [ ] [Onion Service PoW stabilization (#1751) · Issue · tpo/core/arti](https://gitlab.torproject.org/tpo/core/arti/-/issues/1751) * [ ] [PoW: allow toggling enable\\_pow at runtime (#2082) · Issue · tpo/core/arti](https://gitlab.torproject.org/tpo/core/arti/-/issues/2082) * [ ] [Test client PoW in shadow (#1680) · Issue · tpo/core/arti](https://gitlab.torproject.org/tpo/core/arti/-/issues/1680) * [ ] [Test ProofOfWork encoding/decoding (#1679) · Issue · tpo/core/arti](https://gitlab.torproject.org/tpo/core/arti/-/issues/1679) * [ ] [Client PoW: Report detailed error when PoW requested but can't be provided (#1677) · Issue · tpo/core/arti](https://gitlab.torproject.org/tpo/core/arti/-/issues/1677) * [ ] [Limit number of tasks spawned for client proof-of-work (#1676) · Issue · tpo/core/arti](https://gitlab.torproject.org/tpo/core/arti/-/issues/1676) * [ ] On the C Tor implementation, considering issues like the following: * [ ] [Cap received PoW effort values (#41107) · Issue · tpo/core/tor](https://gitlab.torproject.org/tpo/core/tor/-/issues/41107) * [ ] Inform that implementations differ: as of 2025-08, C Tor and Arti implementations are based on distinct control loop algorithms. Point to the relevant Tor specifications. * [ ] Add references to related research: * [ ] "Onions Got Puzzled" attack: * [ ] [Professor Minseok Kang's KAIST Research Team Wins "Outstanding Paper Award" at International Security Conference - The Asia Business Daily](https://view.asiae.co.kr/en/article/2025091207533909856) * [ ] [Onions Got Puzzled: On the Challenges of Mitigating Denial-of-Service Problems in Tor Onion Services | USENIX](https://www.usenix.org/conference/usenixsecurity25/presentation/lee) * [ ] [usenixsecurity25-lee.pdf](https://www.usenix.org/system/files/usenixsecurity25-lee.pdf) * [ ] [sec25cycle1-prepub-343-lee.pdf](https://www.usenix.org/system/files/conference/usenixsecurity25/sec25cycle1-prepub-343-lee.pdf) [DoS guidelines page]: https://community.torproject.org/onion-services/advanced/dos/ [prop362]: https://spec.torproject.org/proposals/362-update-pow-control-loop.html [admonition]: https://squidfunk.github.io/mkdocs-material/reference/admonitions/ [arti-config]: https://gitlab.torproject.org/tpo/core/arti/-/blob/484b9b43a256fc3499de36130905a86274e3366f/crates/arti/src/arti-example-config.toml#L693 # Time estimation * Complexity: very small (0.5 day) * Uncertainty: low (x1.1) * [Reference](https://jacobian.org/2021/may/25/my-estimation-technique/) (adapted) /cc @wesleyac